In-band signaling[1] strikes again. * should not have been used as special value, neither for "no password" in /etc/passwd nor "error while hashing the password" in crypt. I'm afraid we'll find many more of these abuses, specially in string manipulations. The null was ok, an exception (or equivalent) better, and Result<T> (or equivalent) best.
Also how many times do we have to learn that letting badly programmed software die when unexpected things happen is the better option because it means people actually notice that there's a problem. Silent compatibility hacks are the worst, they guarantee problems never get fixed and the stack of hacks never gets smaller.
Microsoft has historically been one of the leaders on the wrong side of this one, but they have also demonstrated how effective it is to call out badly behaved software and make it annoy the users with UAC. When Vista came out, so many applications needed elevated privileges to run because they were badly designed to write user data in system locations, but now their application was more annoying to use and came with a scary dialog about it making changes to your computer that other better-designed software didn't get.
More often than not if a program didn't actually intend to change system settings it was just a matter of badly chosen default paths which are pretty trivial to fix, but so many vendors just would not do it despite years of complaints from NT admins wanting to not have to spend hours with Process Explorer figuring out specific permissions to grant limited users enough access. Once their failures were put front and center, calling their application out as the one getting things wrong every time the user ran it, they suddenly had motivation to fix it.
For security it's better, but in many cases if you're not writing security-oriented software it can be worse from a user perspective. I remember the first job I had over 20 years ago was working on VoD streaming and one of the "tricks" to improve stability was mmap'ing the 0 page so that NULL dereferences wouldn't immediately segfault. Ugly as hell but when you were working with all sorts of more or less well coded media codecs and security wasn't a concern at all (worst case scenario the user would stream movies without paying) it made some amount of sense.
I suspect that Microsoft has the same history: the entire Windows platform was built with single-user PCs in mind, mostly only dealing with trusted input. The users were also expected to be tech-illiterate for the most part and unable to troubleshoot deep technical issues.
More recently I'm still working on video transmission, but on the production side this time. I also originally adopted the mentality that I should crash early if some unexpected situation was encountered, but I ended up walking that back a lot, because having a critical piece of live media production reboot mid FIFA worldcup final is generally Not Great. Degraded functionality is usually preferable. I still crash early in dev builds, but the production code just logs an error and continues if at all possible.
That said, I definitely agree with you for something like password handling. In this case, I do think it's warranted to crash the program without survivors if something is amiss.
> because having a critical piece of live media production reboot mid
It's not great, but these days a trickster with AI will find some way to start broadcasting porn to a billion people because of the flaw, so may end up being the better option.
This is a side-effect of Unix-y "it's all plain text" design that leans extremely heavily upon in-band signalling (among other design decisions).
If /etc/shadow was a JSON (or XML, even, although that would make me feel gross), this bug would have been much easier to see, because a field that reads '"hash": ""' sticks out a lot* more than a custom microformat that you don't understand.
With data structures, there's never "plain text" - it's all structured. The question is whether you want to use existing formats and tools, or create a new one for every tool and literally make footguns like this.
Random parts of it will be interpreted by the shell, others by cURL, or the filesystem, or the remote server. They each have their own encoding rules, nested. I count ten distinct separators and nine ways of escaping/tagging. It's one command. No, just no.
We have seriously overused strings and we're now paying the price.
I'd say another UNIX-y thing - "C is good enough" - is part of the problem. C makes programming painful which results in all sorts of hacks.
E.g. in Pascal you can can define a record and then defined file of record to have typed I/O. I.e. it comes with built-in serialization format supported by compiler. Not a good one - but perhaps a step in a good direction.
OTOH C people starving for serialization often believe that `struct` byte layout made by a specific version of a compiler is a serialization format - a view not endorsed by the standard.
The issue isn't the config, but the fact that crypt() doesn't have any way to signal failure. In better designed languages you would have exceptions, result types, or something. Even in C you have "return integer indicating success or error" which would've prevented the confusion.
Now the public API is hard to change but you could still avoid the issue by returning a longer token like "==DANGEROUS_CRYPT_ERROR_length==" or "==DANGEROUS_CRYPT_ERROR_unsupported_alg==" which would never match the password field unless someone was really trying to induce the issue.
Some badly designed password hashing algorithms (cough bcrypt cough) have maximum password lengths, ignoring everything after X characters. So it could happen that I set my password to a 100-character string, it gets saved as "==DANGEROUS_CRYPT_ERROR_length==", and then anybody can log in to my account by entering an unrelated long string that returns the same "error".
If a function promises a string result, it should only provide a string if the function succeeded. The null was much better than magic strings.
I know, it's bad. I agree that it should've stayed NULL. But if you really really really think you have an acceptable reason to do something like this (and you probably don't), the least you can do is use a non-trivial token.
At this point I’m resigning myself to think that we’ve just gotta wait for some people to die. It feels very dramatic and glib (no pun intended lol) and whatever to say, but at this point it feels like there’s a certain hostility in some parts to changing anything from the platonic ideals of however computing happened to work in 2004. “Oh we don’t need to mess with it!”
I think this is a bit unfair. The way I see it, a lot of people are saying that changing breaks lots of old stuff, and risks complete fragmentation. Those are real costs to change. It might still be worth it, but let's not pretend that everyone is resisting change just because it's change.
PSA: you can typically declare different types of string so that your type system objects to mixing data of that type even though deep down we know they're both strings.
- (note root won't work by default because of PermitRootLogin prohibit-password default)
- attempt twice, first attempt fails second long password is accepted (that took me a while to understand)
In practice passwd -l seems to lock with a ! prefix, and new account without passwords are created with a single ! which is also not affected, I'm not sure how big the impact actually will be in practice and don't understand the recommendation to upgrade urgently right now... Just don't use `*`?
EDIT: ah, some default container images apparently have a default alpine user with that hash, so I guess that's bad for them. This makes a bit more sense now.
Well but, alas, a non-zero number of user probably do use it, though and "upgrade X" is a clearer and better instruction to communicate than "change this setting where maybe you don't even know what it means and it might break your workflow, but saves you an upgrade".
You have considerably underestimated both how fallible humans are, and how high their tolerance is for risks which aren't immediately visible.
This isn't even just the software industry, humans are like this about everything. Imagine explaining to something rational that (a) humans didn't realise that they won't be able to competently operate a motor vehicle while watching TokTok dances, and (b) when we finally made that illegal because it's such an obviously bad idea they would keep doing it anyway.
This is why those "What if it builds SkyNet?" conspiracies were so stupid. Why on Earth would you build SkyNet when you can just invent Weeaboo and the idiot humans will die playing ?
True, but also, that is exactly the pretext that would allow someone to maliciously, intentionally commit a backdoor.
There was even a contest for hiding/obfuscating malicious code, e.g. as an honest mistake: https://www.underhanded-c.org/ . And what do you know, the most recent, common approach shown on the page, is: improper comparison inputs that give unexpected comparison results, which is... well... this submission.
Pretty big? For this purpose, my instinct would be to select an ASCII character that's not alphanumeric, not directional, and not a common separator, and that's like, what, a set of 11 characters?
Never attribute to malice that which yada yada yada
And like who even needed to plant back doors? If you're the NSA you already had an agent swarm in 1993, but it was made out of dudes from Berkeley and New Haven instead of racks in Prince William County and 印材 (and they were literal secret agents I guess, pretty metal). You can get back doors just by foraging, no need for agriculture.
Above all, I’m a little sad that the musl developers decided to make a lot of “well it’s convenient” changes to core crypto functions — at least without the level of auditing that would have caught this! It’s tarnished their reputation in my eyes a little.
I think everyone is over fixated on AI finding complex bugs beyond a typical person's understanding either to locate or exploit.
I think for any one of those bugs there might simply be half a dozen footguns or bugs that once it's spelled out you wonder how anyone let it slide.
I think that's the case where LLMs might indentify most.
It's challenging though as the current AI audits produce so many false positives it's hard to know when it's being pedantic or when it's genuinely caught a human being a bone head
Finding more and more that these complex bugs people gloss over like you are now are being used in exploit chains and the end result is still my clients getting hacked
A little?!? I’m sorry, but musl is a joke, this is yet another proof of that fact, and I have no idea why anyone uses it in production, they have only themselves to blame after the many warning signs.
In many ways each individual decision makes some sense;
wanting to stop loads of programs being affected by a (remotely triggerable?) crash
wanting to avoid time based attacks
wanting to be able to set accounts to not have a password
Each one relies on a perfectly valid argument - that * can't match because we all know it'll be rejected by the other thing.
Rust and go still make it pretty easy to not check results if you don’t care about the success value (lots of code just does `let _ = foo()`), but if you do want the value (like with a hashing function), Rust makes it really hard to not check the error too. There’s no syntax to say “assume this worked and give me the success value, including whatever garbage is there if it’s not set”:
- result.unwrap() will panic if it failed
- result.ok() throws away the error but gives you a None value instead (still can’t use it as if it’s a success)
- matching on the Ok variant and doing nothing on the Err variant, you only get to use the success value inside the Ok arm
Etc etc.
The problem is when the compiler says “NULL is a valid instance of T”, which go lets you do, and rust doesn’t (without using the unsafe keyword and intentionally casting a null pointer, which you don’t do by accident.) Go lets you write code like `var hash string; hash, _ = hashfn()` and it compiles and now you have null instead of a valid hash.
Any use of sum types would have prevented this immediately.
The whole thing exists because APIs that return a NULL value that "nobody checks", plus a string that you shouldn't use if you actually did check the null value.
In languages with sum types, this cannot happen.
Either you get your hash, or no result at all.
You couldn't get eg NULL and *.
Yet the authors of crypt did not use them. The C language is not designed in a way to encourage people to write code that correctly uses tagged unions (or nullable pointers for that matter).
means that most ways of returning an error from a function are not available in C. Because of this, many C APIs, including `crypt` in this case, resort to in-band error signalling by using a sentinel value (like NULL, a negative integer, "*" etc.).
Most other languages lack one or two of the above, but very few lack all three, and so most have developed a different culture around error reporting (Result in Rust, multiple return values in Go, exceptions in Java, Python etc.).
One of the small but important significances of Rust is that it very often gets to have the same machine code as a correct "in-band error signalling" strategy from C but with source code that the maintainers can actually understand.
And really often when your "in-band error signalling" in Rust is more expensive you realise (perhaps to your horror) that your C wouldn't be correct, so you just dodged a bullet. For example Option<OwnedFd> is, like OwnedFd, a 32-bit value, Unix has always reserved -1 to mean invalid, so Rust can treat that as a niche. But the Windows equivalent Option<OwnedHandle> can't do this because, well, cue Raymond Chen: https://devblogs.microsoft.com/oldnewthing/20040302-00/?p=40...
I would be more concerned about the lack of explicit return types, one of the arguments for strongly typed languages is that you should not have ambiguous data and yet…
Granted I mostly work with high level programming languages so I may be missing something.
You must be new here. While I applauded the idea of musl when it first came out (coincidentally, glibc wasn't having the best time in its development then), the developer's arguments why <some behavior drastically different from every libc under the sun> was akchyually correct, which was why you had to fix a program that hadn't been broken for 30 years and now suddenly was, made me put him under the "clowns" category and never look at musl seriously again.
When later it turned out that musl's procrustian stack size made Python not really runnable under it, it cemented my resolve to not go near musl.
I’m also reminded of the clowns pushing “it’s smaller!” container images based on social media vibes rather than analysis where, yes, not using Debian+glibc saved tens of megabytes on the base OS but did so at the expense of measurable performance reductions & compatibility issues like the one you mentioned, and literally every single one of those dudes I worked with was shipping containers pushing a gigabyte so the size reduction had no measurable impact on deployments.
OK, I think I see what’s going on with this, in this configuration.
The goal from an attacker’s perspective is to get this to be true: `$ret = crypt($pw, $hash); $ret == $hash` when called by OpenSSH’s sshd. This is how sshd validates that the user logging in knew the account password.
The `$hash` is the “settings” to the crypt call and will normally look like “$6$--gibberish” for users with passwords set, but could look like “*” or “!” for users not intended to be able to login.
The bug is from the intersection of all of these things:
1. musl can return “*” for errors, rather than leave the return value NULL. Other libc have adopted something like this too, but seem to use a different result “*0”.
2. musl can also return “+” for errors, but only does so if $hash starts with “*”. This is intended to eliminate the possibility of an error causing `$ret == $hash` to be true, however it assumes that applications calling `crypt()` will set $pw and $hash to values corresponding to the `$ret == $hash` comparison to be made immediately afterwards.
3. OpenSSH can be convinced to pass the hash of a different user if the hash is “*” or “!” to avoid timing attacks that can enumerate the user list, so it will set $pw and $hash to correspond to different users. $hash will be a real “$6$--gibberish” style hash in this case, and OpenSSH expects `crypt()` to either return NULL or return a hash string. But now there’s two hashes OpenSSH uses. It does: `$ret = crypt($pw, $hash2); $ret == $hash1`;
4. This should normally not be a problem because OpenSSH will pass in valid $pw and $hash2 that should not lead to errors in hashing, so the $ret that musl generates should be a real hash that cannot match the “*” or “!” $hash1 for the login-disabled user. However as a DDoS mitigation, musl will return error if the password is too long when using SHA-2-based hashes (the default, it seems).
5. This error will result in a non-NULL result of “*” or “+”. Since OpenSSH passed in a real hash ($hash2), musl will return “*”, which compares equal to the actual user hash $hash1 for the disabled-login user.
The OpenSSL adjustment ensures a minimum hash length for the user before logging them in, even if crypt() succeeds somehow.
Because Claude wrote the linked page. Claude is impressively bad at communicating these days. with gpt-5.6+ approaching Claude level like 30% of time and Gemini much clearer but also the most annoying 7 year old ever, it’s a pretty lame environment especially for people who r new to everything
I was able to reproduce this on Alpine 3.23.7 with OpenSSH_10.2p1.
Luckily PermitRootLogin [0] hasn't allowed logins with passwords for root since 2015 [1]. I'm guessing that's at least part of why this went undiscovered for so long.
Did anyone get it to work? I tried on the official alpine docker image, enabled password login for root. The shadow entry has ! as password by default, this didn't work with a > 256 character password (i also did passwd -l which also does !). I manually changed it to * and it still didn't work.
In Alpine, these would all be the case for an out of the box install with openssh added unless you specifically install openssh-server-pam and configure sshd_config to use PAM (Alpine is already musl-c based and doesn't default to PAM).
Doesn't it also need a user to be added with a password entry?
I only ever see Alpine Linux used for containers which don't need accounts with interactive user logins, which is not to say it doesn't exist, just that it doesn't seem like Alpine comes with all preconditions met out of the box
No, didn't work for me open OpenWRT x64 running in a container but that is probably 'cause I'm using dropbear instead of openssh-server. That's what OpenWRT uses by default so the impact there will be minimal assuming that most installations don't change to openssh-server - it isn't installed by default.
Ahh! Wasn't working on 3.16, which does indeed have an updated package.
But, got it to work on 3.15 - which requires changing the ! to a * in the shadow file in addition to other steps (making another user with a hash, setting PermitRootLogin to yes, etc.).
I can't reproduce it either. I used alpine:3.24.1 and openssh is openssh-server-10.3_p1-r2
I tried adding PermitRootLogin yes and PasswordAuthentication yes. Tried adding another user with a valid password.
Verified shadow entry has a *. Can't login as root or a test user. Tried another incorrect password first as well.
edit: can reproduce after `git revert 384e25e6bd1f2e7b30095900e48b570d46953510` in aports and rebuilding openssh without the fix. It also accepts the password on the 2nd+ attempt, NOT the first.
Offtopic: this is a very cool way to present commits and code excerpts. Love classic Windows styling.
Were those pictures with links generated using a publicly available tool that we could use, or were it custom (vibe)coded specifically to create this page?
Yes, correct for OpenWrt. OpenWrt defaults to dropbear for both server and client. However, more advanced users may optionally choose to replace it with OpenSSH, or install OpenSSH side-by-side, to gain additional features of OpenSSH.
I'm starting to realize that trusting some random people who wrote the gruddiest, boringest, most torturous low-level stuff might have been a bad plan.
At this point I feel embarrassed in front of the AIs.
Maybe that's on you though. I enjoyed it, though the discrepancy between the `*sshole` name and the `sshhole.com` domain made me twitch. How is anyone[0] obsessive enough to find this and write it up and yet not obsessive enough to make the amount of `h` consistent?
[0]: Be they human or LLM. Or an entity with any proportion of the two. I do not judge nor discriminate.
Wow. I wonder which of the common fuzzers would have found this a decade ago. If literally any password over 256 chars works, that means nobody has ever fuzzed openssh on musl linux
The last few weeks have made me feel very good about my policy of zero internet-accessible ssh ports, ever. On AWS, use SSM. For a VPS or home server, access everything over WireGuard.
Edit: Sure, a small minority presumably run sshd under these conditions. But a small minority times the number of Alpine containers running in the world gets to a large absolute number.
Edit 2: You really don't need to look very hard to find public container examples at million-download scale.
Many, many Docker containers rely on "docker exec" or the kubectl equivalent to gain CLI access when needed. To have sshd in an Alpine Docker container, you're generally need to be running init and a bunch of demons, not just a single standalone service.
I'm guessing in practice relatively few people are actually exposed. But if they are, it's catastrophic.
What is out there that uses musl without PAM and hosts an OpenSSH SSHd with PasswordAuthentication?
Possibly public SFTP servers. I have allowed null passwords in the past for anonymous public SFTP and I run Alpine Linux exclusively for my servers both VM's and physical. The shadow package (PAM) did not get installed by default. I installed it but I had to specify it in the installation so there are likely people without it. There is probably a way to find them on shodan.io.
I will activate one for people to play around with for today:
sftp hn@ping.ohftp.org
There's no firewall and no password. Hack away HN.
It's amazing how similar this exploit payload is to the 20+ year-old Quake 3 vulnerabilities found by Luigi Auriemma (aluigi), which also used the exact same 256-to-1024 character range and nothing more than a long string of AAAA.... Here you're feeding >256 A's up to a 1024-byte limit to trip musl's defensive length cap, whereas back in the mid-2000s, Luigi was famous for publishing one-line .cfg scripts where the entire exploit was literally "say aaaaa..." repeated a few hundred times overflowing server's memory.¹ ²
A great example is Jedi Academy, a 2003 Quake 3 engine game whose multiplayer is still actively played today (its open-source engine port, openjk, is even in the Debian repos btw). Luigi had two classic scripts for it on his site: Jedi Academy <= 1.011 in-game server buffer-overflow (jamsgbof)¹, which crashed the server just by pushing a string of as past the 1024-byte console buffer, and Quake 3 engine in-game players kicking (q3msgboom)², where a wall of as hit the engine's 1022-char truncation limit and the leftover bytes confused the parser into disconnecting everyone on the server.
Kind of wild that 20 years later, the exact same payload goes from crashing Quake 3 matches from the tilde console to getting root on some SSH servers.
To be fair, I have less than zero sympathy for anyone who runs SSH on any platform without `PasswordAuthentication=no` in 2026.
Its not asking for trouble, it is there will be trouble, not if but when.
As for the people who say "well, I run SSH on port 942329053052". Well guess what, the bots make short work on that. We tried it at $work as an experiment, multiple bots found it in less than a couple of hours. That's why your SSH config must be hardened, preferably running on a hardened OS too.
The exploit works for a user account that has no password. This is often confused with turning off password auth, especially in containers that have only one usable account.
It's not just the parent commenter. I'm sure somebody out there is going to remove their account password instead of editing their sshd_config in an attempt to "patch" this vulnerability, actually exacerbating the problem.
Bug > are password logins still on? they are by default
You > This particular bug works even with password authentication turned off.
No. The bug is related to password authentication. If you do not have password authentication then you are not affected.
What freaks some people out is they chose parameters where they do have password authentication but they expect to always fail. That's a bad choice, like OK you did fit a cheap manual keyhole, but you threw the keys away thinking now nobody can open that - you realise somebody with a cheap jiggler can open it right ?
How is password auth weaker than key auth? Bugs in auth code can happen in both pathways. And apart from stupidly short passwords both should be equally impossible to brute-force.
In other words, conceptually, at the end if the day, isn’t a key just another name for a password, really?
What people think of as a very strong password often has <100 "security bits" of entropy.
Keys are usually at least 128 bits of entropy, and it's easy to take them up to 256.
Yes, both are a shared secret, but password auth - even with challenge-response - is weaker than key auth exactly because key auth provides more guess resistance.
Huh? I run ssh (OpenSSH) on port 22 with root login enabled and no fail2ban on a single-core laptop cpu from fifteen years ago. The load average is 0.00 even with the small mail and web server that runs on it
What cpu and especially what disk load are you talking about? Also not running out of sockets, not sure if that's RAM-dependent (the box has 2GB)
Worth noting that if you are running a remotely recent version of SSH it has everything you need built-in. No need for Fail2Ban on SSH these days if your config is fully modernised.
Password gets sent to the server. Private key does not get sent to the server, and authentication protocol can be forwarded safely, enabling things like ssh-agent, FIDO SSH keys. This is solvable with passwords (see: augmented PAKE), but `PasswordAuthentication` isn’t that. But there are also settings where none of this really matters, yes, to be fair if that’s what you’re referring to.
> password doesn’t get sent to the server, hash does.
Kind of irrelevant what gets sent to the server and what happens on the server.
Password is already easily defeatable long before it even leaves your computer, thanks to keyloggers and/or password manager breaches and/or old-school shoulder surfing (assisted in the 2026 era by covert filming and AI).
All of which are not vulnerabilities with hardware-backed keys which you don't even need a Yubikey for these days since most modern computers and smartphones have secure enclaves and/or TPMs. (Yubikeys are still great though).
No, you are wrong. The password gets sent to the server. That said, I still enable passwords on servers, but don't ever share passwords between trust domains.
Same issue with key reuse. Unless you have a policy to rotate them and verify which host they login from, someone's unencrypted hard drive from 5 years ago is more likely to have a key than password.
> someone's unencrypted hard drive from 5 years ago is more likely to have a key than password.
Even 5+ years ago, hardware-backed SSH keys were a thing (Yubikey). The only difference today is that its 100% easier to do keys properly because of the widespread commoditisation of secure enclaves in desktops and smartphones to support FIDO, its basically free of charge now because you're not obliged to buy a Yubikey.
Even if you don't want to go all the way to SSH certificates, SSH public-key authentication is laughably easy to do.
I also don't buy the argument "but its on a ULA address". Attacker's old favourite these days is finding a way in (North–South) and then using that as a stepping stone (East–West). Also the general concept of "lower security is OK because its on the LAN" is so 1997.
Yeah because if attackers are already finding a way in, they can easily read my ~/.ssh/id_ed25519. A password is strictly better, although not by much because lateral movement is very easy anyways. The only exception is if the private key is actually on a HSM, which is the case for all my SSH private keys on iOS.
> Its not asking for trouble, it is there will be trouble, not if but when.
Did any of those bots brute force a password? Because a 20 character random password is comparable in brute force complexity to an SSH key. The experiment you ran was just as valid for SSH keys on that port, and had no bearing on password vs key.
The point is they found the security by obscurity so-called "hidden" port in less than a couple of hours.
At that point, what they did is irrelevant. The point is that security by obscurity does not work in 2026.
> Because a 20 character random password is comparable in brute force complexity to an SSH key.
You can't be serious with your comment.
No its not.
And even then, SSH key is asymmetric, you're not sending the private key to the server. But with a password you are, which leaves you vulnerable to many attack vectors that simply do not exist with keys.
This is a sampling error - we're only hearing about the public disclosures.
(almost) No company actually has secret source code, only source code not publicly viewable. And the LLMs crawling those don't belong to people who make public disclosures.
> > Because a 20 character random password is comparable in brute force complexity to an SSH key.
> You can't be serious with your comment. \n\n No its not.
If you differ in opinion, maybe provide evidence? Especially for a claim like long randomly generated value 1 being absurdly ("can't be serious"-level) weak as compared to long randomly generated value 2
If you mean it's log(62^20,2)≈119 bits of entropy instead of 128+ and so it's theoretically weaker when we build a Dyson sphere around the sun to brute force that key (after somehow obtaining the shadow file, since an online attack would be way too slow), then sure
PSA for OpenWrt users: If you are getting the post quantum message on login which points to openssh.com, you are likely using dropbear nonetheless. Check in System->Software. I was confused and worried why I seemingly had the vulnerable OpenSSH installed, but its just dropbear using an OpenSSH link.
Did we declare "break the world Thursday" and nobody told me? I feel like it's three weeks in a row that we've had a once-in-a-decade security issue pop up.
Thanks you to the team that found this. Exceptionally well explained and funny at the same time. What is most important is how people just checking stuff( remember the .xz hack that was tried?) has save the internets ass so many times. We should give good security researchers UBI for life for just doing good work.
The bugs and commits that "fix" them reveal somewhat of a shitshow for how musl is managed. All projects have bugs, but I can't help but question why the wheel was reinvented here. Many toes have been stubbed along the way.
I avoided using alpine-based containers ever since finding out a lot of Linux server software is actually Linux + SystemD software. The union set API of both Linux and SystemD seems to be the default "Linux API" today.
That's their point. The software they want to use often assumes its being run on a platform with systemd, so running that software on Alpine which makes a point to not use systemd causes challenges for them compared to using a different distro.
This is a super duper annoying site for people who just want to know if their systems are vulnerable, after patching like a dozen critical vulnerabilities in other software over the last week and are almost at the breaking point of resigning.
Can we have a “don’t treat me like five/toddler” / “idgaf about the explanation” quick link to a section for adults who need to patch systems?
(And if your reaction is “just scroll down, stupid”, I’m happy to report that with the scroll jacking, I scroll not enough / past the critical sections nine out of ten times.)
Thanks for mentioning that before I tried to scroll down. Forewarned, I was able to click on the "2026" link once the left-handed "scrollbar" (not the right word but I can't figure out what the right word should be) appeared, which let me jump past most of the verbiage and get to the "are you affected?" section just a couple pages later.
Not the worst site, but it's clearly a publicity machine from wakefield.co, whom I haven't heard of.
Also, exploitation conditions are super narrow, albeit, any password is wild.
> except a lot of programs never check for NULL. they just compare whatever crypt() gives back with the stored field, hit the NULL, and crash
> so musl (the libc under alpine) goes ok fine, crypt() just won't return NULL anymore. if it fails, it returns a single character instead.
Considering it's been accepted that crashing if malloc returns a NULL is your fault, did musl really feel the need to accommodate bad implementations like this or is this just AI speculation?
> did musl really feel the need to accommodate bad implementations like this
I don't know about this specific case but in general? Yes, totally. No one is going to fix all existing software that depends on libs behaving exactly as glibc, you have to accept some trade-offs. Either your new implementation stops being perfectly simple and clean, or no one uses it.
"unfortunately, a large portion of programs which call crypt are not
prepared for its failure and do not check that the return value is
non-null before using it. thus, always "succeeding" but giving an
unmatchable hash is reportedly a better behavior than failing on
error." [1]
Such a questionable decision! "Rather than let a bug in a caller (not handling the valid null output and thus crashing) surface, let's just silence it and pretend that the caller is correct! A potential clash in some situations (resulting in this vulnerability) is better than a crash!"
Maybe I should update my plea to fail loudly (https://alejo.ch/3gk) to list this as an example.
> how did I ran into it? [...] i had agent swarms. a lot of them. let's not get into it
Can we please now normalize AI usage in development? Just some other day people asked for "NO AI used" badges for software as measure for quality, and praised i.e. NetBSD for being AI-free. Yes, we come from a phase of AI slop, but it has become obvious that there are plenty of legit usecases where AI beats human-only effort nowadays.
Not sure why but a lot of people seem to be missing that you don't have to look at AI as a binary "you're either with us or you're with the terrorists."
Just do HITL (human in the loop). Use an LLM to help you author, but steer the AI in whatever direction you want. It's like having a slightly delusional copy of yourself to pair program with. If you take the time to provide an LLM with some additional skills files and the like, with you in the pilot seat, you can get solid results (it doesn't look as cool as a hands free agent setup but the quality far surpasses anything they can do solo).
> Can we please now normalize AI usage in development?
1. It is already normalized outside of a tiny, but very vocal bubble that lives mostly on Bluesky (sometimes also on Reddit/HN/Mastodon).
2. I don't think that even the most staunch AI hater would object to using AI for security research as long as all the artifacts (code, docs) that were produced based on the research are human-written. "Yes, there is a bug in my program, but I refuse to fix it, because I know that you found it using AI" would be a pretty weird position. Not sure, how would you defend it.
It's shocking that it took so long with the amount of investment and hype you'd expect this kind of bugs to be already fixed, but it still need a human to tell the agents what to do, which could also work with any fuzzing framework
Can we just have a site with the text and images without the awkward scrolling crap? Hijacking basic features is an instant click away from sites for me
Edit: It seems to work fine on mobile. I'm not sure why the scrolling behaviour was added on the desktop version of the site
I think it varies from person to person. Since I'm kind of from the TikTok generation, I don't have much trouble reading this kind of animation, but some people prefer static sites. That's just how it is.
I also found scroll-triggered animations hard to read at first, but these days a lot of sites use them, so I've gotten used to them.
Yep, scrolling through my phone and reading slowly to understand. I'm seeing distracting animations below what I'm reading. And when I go to them, there is no way to restart them. So it completely misses the point.
Yet another clankered finding creating a clankered website with clankered explanations. To be fair, this one's a lot better than the other clankered equivalents, but I wonder whether these people even know enough about their bug to have their own write-up?
Also, what's with this damn trend of typing in lowercase only? Why is this a thing?
> oh did i say "i"? sorry. i had agent swarms. a lot of them. let's not get into it
Still a cool finding... it's just the communication is becoming a lot worse these days - I want to understand the findings please, not be impressed by your webpage! Biggest gripe in recent memory is https://github.com/xoreaxeaxeax/skitter-creek-bath-salts
sigh, it's not a new trend. it's just yet another pop-cultural appropriation from the gay community, now mainstream thanks to ai. as trump's gay dementia progresses, pretty soon even he will be truthing about other men's asses in lowercase, just to get a rise out of them!!! however, the *sshole project's shibboleths of lowercasing and anal asterisk punctuation strongly suggest its authors may be bona fide members of the lgbtq+ community.
> Let’s sit and twink about the data. 24.6% of my 19,000+ respondents abandoned capitalization entirely. If you control for age, queer people were 1.5x more likely than straight people to type in lowercase. Lesbians out-lowercased every other sexuality at 28.3%, followed by bisexuals at 24.9%. Honorable mention to the lowercase enbies, at 29.2%.
New and Changing Social Evaluations of All-lowercase and Exclamation Points
In-band signaling[1] strikes again. * should not have been used as special value, neither for "no password" in /etc/passwd nor "error while hashing the password" in crypt. I'm afraid we'll find many more of these abuses, specially in string manipulations. The null was ok, an exception (or equivalent) better, and Result<T> (or equivalent) best.
[1] https://en.wikipedia.org/wiki/In-band_signaling#Computer_dat...
Also how many times do we have to learn that letting badly programmed software die when unexpected things happen is the better option because it means people actually notice that there's a problem. Silent compatibility hacks are the worst, they guarantee problems never get fixed and the stack of hacks never gets smaller.
Microsoft has historically been one of the leaders on the wrong side of this one, but they have also demonstrated how effective it is to call out badly behaved software and make it annoy the users with UAC. When Vista came out, so many applications needed elevated privileges to run because they were badly designed to write user data in system locations, but now their application was more annoying to use and came with a scary dialog about it making changes to your computer that other better-designed software didn't get.
More often than not if a program didn't actually intend to change system settings it was just a matter of badly chosen default paths which are pretty trivial to fix, but so many vendors just would not do it despite years of complaints from NT admins wanting to not have to spend hours with Process Explorer figuring out specific permissions to grant limited users enough access. Once their failures were put front and center, calling their application out as the one getting things wrong every time the user ran it, they suddenly had motivation to fix it.
For security it's better, but in many cases if you're not writing security-oriented software it can be worse from a user perspective. I remember the first job I had over 20 years ago was working on VoD streaming and one of the "tricks" to improve stability was mmap'ing the 0 page so that NULL dereferences wouldn't immediately segfault. Ugly as hell but when you were working with all sorts of more or less well coded media codecs and security wasn't a concern at all (worst case scenario the user would stream movies without paying) it made some amount of sense.
I suspect that Microsoft has the same history: the entire Windows platform was built with single-user PCs in mind, mostly only dealing with trusted input. The users were also expected to be tech-illiterate for the most part and unable to troubleshoot deep technical issues.
More recently I'm still working on video transmission, but on the production side this time. I also originally adopted the mentality that I should crash early if some unexpected situation was encountered, but I ended up walking that back a lot, because having a critical piece of live media production reboot mid FIFA worldcup final is generally Not Great. Degraded functionality is usually preferable. I still crash early in dev builds, but the production code just logs an error and continues if at all possible.
That said, I definitely agree with you for something like password handling. In this case, I do think it's warranted to crash the program without survivors if something is amiss.
> because having a critical piece of live media production reboot mid FIFA worldcup final is generally Not Great.
Story time?
> because having a critical piece of live media production reboot mid
It's not great, but these days a trickster with AI will find some way to start broadcasting porn to a billion people because of the flaw, so may end up being the better option.
> Microsoft has historically been one of the leaders on the wrong side of this one
Objective-C ahem nil messaging...
Objective-C is an Apple thingie :)
By way of NeXTSTEP
This is a side-effect of Unix-y "it's all plain text" design that leans extremely heavily upon in-band signalling (among other design decisions).
If /etc/shadow was a JSON (or XML, even, although that would make me feel gross), this bug would have been much easier to see, because a field that reads '"hash": ""' sticks out a lot* more than a custom microformat that you don't understand.
With data structures, there's never "plain text" - it's all structured. The question is whether you want to use existing formats and tools, or create a new one for every tool and literally make footguns like this.
Yes, absolutely. Take for example this cURL command:
Random parts of it will be interpreted by the shell, others by cURL, or the filesystem, or the remote server. They each have their own encoding rules, nested. I count ten distinct separators and nine ways of escaping/tagging. It's one command. No, just no.
We have seriously overused strings and we're now paying the price.
Also: free text is the input format of LLMs...
I'd say another UNIX-y thing - "C is good enough" - is part of the problem. C makes programming painful which results in all sorts of hacks.
E.g. in Pascal you can can define a record and then defined file of record to have typed I/O. I.e. it comes with built-in serialization format supported by compiler. Not a good one - but perhaps a step in a good direction.
OTOH C people starving for serialization often believe that `struct` byte layout made by a specific version of a compiler is a serialization format - a view not endorsed by the standard.
The issue isn't the config, but the fact that crypt() doesn't have any way to signal failure. In better designed languages you would have exceptions, result types, or something. Even in C you have "return integer indicating success or error" which would've prevented the confusion.
Now the public API is hard to change but you could still avoid the issue by returning a longer token like "==DANGEROUS_CRYPT_ERROR_length==" or "==DANGEROUS_CRYPT_ERROR_unsupported_alg==" which would never match the password field unless someone was really trying to induce the issue.
No, that's just more in-band signaling!
Some badly designed password hashing algorithms (cough bcrypt cough) have maximum password lengths, ignoring everything after X characters. So it could happen that I set my password to a 100-character string, it gets saved as "==DANGEROUS_CRYPT_ERROR_length==", and then anybody can log in to my account by entering an unrelated long string that returns the same "error".
If a function promises a string result, it should only provide a string if the function succeeded. The null was much better than magic strings.
I know, it's bad. I agree that it should've stayed NULL. But if you really really really think you have an acceptable reason to do something like this (and you probably don't), the least you can do is use a non-trivial token.
At this point I’m resigning myself to think that we’ve just gotta wait for some people to die. It feels very dramatic and glib (no pun intended lol) and whatever to say, but at this point it feels like there’s a certain hostility in some parts to changing anything from the platonic ideals of however computing happened to work in 2004. “Oh we don’t need to mess with it!”
I think this is a bit unfair. The way I see it, a lot of people are saying that changing breaks lots of old stuff, and risks complete fragmentation. Those are real costs to change. It might still be worth it, but let's not pretend that everyone is resisting change just because it's change.
The costs to change are dropping significantly with AI.
Citation needed.
PSA: you can typically declare different types of string so that your type system objects to mixing data of that type even though deep down we know they're both strings.
So to recap, with a non-upgraded sshd you need:
- an account with /etc/shadow hash set to '*'
- (note root won't work by default because of PermitRootLogin prohibit-password default)
- attempt twice, first attempt fails second long password is accepted (that took me a while to understand)
In practice passwd -l seems to lock with a ! prefix, and new account without passwords are created with a single ! which is also not affected, I'm not sure how big the impact actually will be in practice and don't understand the recommendation to upgrade urgently right now... Just don't use `*`?
EDIT: ah, some default container images apparently have a default alpine user with that hash, so I guess that's bad for them. This makes a bit more sense now.
> Just don't use `*`
Well but, alas, a non-zero number of user probably do use it, though and "upgrade X" is a clearer and better instruction to communicate than "change this setting where maybe you don't even know what it means and it might break your workflow, but saves you an upgrade".
At this point it feels to me we aren’t discovering security bugs but a decade of planted backdoors.
You have considerably underestimated both how fallible humans are, and how high their tolerance is for risks which aren't immediately visible.
This isn't even just the software industry, humans are like this about everything. Imagine explaining to something rational that (a) humans didn't realise that they won't be able to competently operate a motor vehicle while watching TokTok dances, and (b) when we finally made that illegal because it's such an obviously bad idea they would keep doing it anyway.
This is why those "What if it builds SkyNet?" conspiracies were so stupid. Why on Earth would you build SkyNet when you can just invent Weeaboo and the idiot humans will die playing ?
True, but also, that is exactly the pretext that would allow someone to maliciously, intentionally commit a backdoor.
There was even a contest for hiding/obfuscating malicious code, e.g. as an honest mistake: https://www.underhanded-c.org/ . And what do you know, the most recent, common approach shown on the page, is: improper comparison inputs that give unexpected comparison results, which is... well... this submission.
> humans didn't realise that they won't be able to competently operate a motor vehicle while watching TokTok dances,
Not everyone is like your sister and mother.
actually this looks very underhanded indeed, what are the odds they pick the same sentinel character?!
Like 1 in 5? The set of go-to characters for that kind of thing is pretty small.
Pretty big? For this purpose, my instinct would be to select an ASCII character that's not alphanumeric, not directional, and not a common separator, and that's like, what, a set of 11 characters?
Be careful, saying this gets you downvoted like https://news.ycombinator.com/item?id=50364646
Never attribute to malice that which yada yada yada
And like who even needed to plant back doors? If you're the NSA you already had an agent swarm in 1993, but it was made out of dudes from Berkeley and New Haven instead of racks in Prince William County and 印材 (and they were literal secret agents I guess, pretty metal). You can get back doors just by foraging, no need for agriculture.
Above all, I’m a little sad that the musl developers decided to make a lot of “well it’s convenient” changes to core crypto functions — at least without the level of auditing that would have caught this! It’s tarnished their reputation in my eyes a little.
I think everyone is over fixated on AI finding complex bugs beyond a typical person's understanding either to locate or exploit.
I think for any one of those bugs there might simply be half a dozen footguns or bugs that once it's spelled out you wonder how anyone let it slide.
I think that's the case where LLMs might indentify most.
It's challenging though as the current AI audits produce so many false positives it's hard to know when it's being pedantic or when it's genuinely caught a human being a bone head
Finding more and more that these complex bugs people gloss over like you are now are being used in exploit chains and the end result is still my clients getting hacked
A little?!? I’m sorry, but musl is a joke, this is yet another proof of that fact, and I have no idea why anyone uses it in production, they have only themselves to blame after the many warning signs.
In many ways each individual decision makes some sense; wanting to stop loads of programs being affected by a (remotely triggerable?) crash wanting to avoid time based attacks wanting to be able to set accounts to not have a password
Each one relies on a perfectly valid argument - that * can't match because we all know it'll be rejected by the other thing.
> Each one relies on a perfectly valid argument - that * can't match because we all know it'll be rejected by the other thing.
But that's not a perfectly valid argument, and it never was.
The real problem here is the C language. Our industry should have dumped it a long time ago and we’re now paying the price of prevarication.
There is no industry, it's just people
Which of the several flaws in this bug chain would have been materially different with a language other than C?
Wouldn't Rust's Result or Go's error checking prevent that?
While not mandatory, a person would probably use it instead of the * hack.
Simply because the calling side wouldn't have an option to forget the check like with the NULL case
Rust and go still make it pretty easy to not check results if you don’t care about the success value (lots of code just does `let _ = foo()`), but if you do want the value (like with a hashing function), Rust makes it really hard to not check the error too. There’s no syntax to say “assume this worked and give me the success value, including whatever garbage is there if it’s not set”:
- result.unwrap() will panic if it failed
- result.ok() throws away the error but gives you a None value instead (still can’t use it as if it’s a success)
- matching on the Ok variant and doing nothing on the Err variant, you only get to use the success value inside the Ok arm
Etc etc.
The problem is when the compiler says “NULL is a valid instance of T”, which go lets you do, and rust doesn’t (without using the unsafe keyword and intentionally casting a null pointer, which you don’t do by accident.) Go lets you write code like `var hash string; hash, _ = hashfn()` and it compiles and now you have null instead of a valid hash.
> NULL is a valid instance of T
This by the way is Tony Hoare's famous "Billion Dollar Mistake"
Any use of sum types would have prevented this immediately.
The whole thing exists because APIs that return a NULL value that "nobody checks", plus a string that you shouldn't use if you actually did check the null value.
In languages with sum types, this cannot happen.
Either you get your hash, or no result at all. You couldn't get eg NULL and *.
C has unions. C has sum types. People have been doing tagged unions in C for longer than rust has been a language
Yet the authors of crypt did not use them. The C language is not designed in a way to encourage people to write code that correctly uses tagged unions (or nullable pointers for that matter).
I don't think I've ever seen a C function that uses unions for this purpose though?
I can think of two common patterns that I've seen frequently:
* Return NULL for errors (sometimes with a global errorno() function).
* Return an integer error with any return values as out parameters.
So if it is possible to improve, why doesn't anyone do it?
C's lack of all of
- sum/union types
- multiple return values/tuple types
- exceptions
means that most ways of returning an error from a function are not available in C. Because of this, many C APIs, including `crypt` in this case, resort to in-band error signalling by using a sentinel value (like NULL, a negative integer, "*" etc.).
Most other languages lack one or two of the above, but very few lack all three, and so most have developed a different culture around error reporting (Result in Rust, multiple return values in Go, exceptions in Java, Python etc.).
C has sum types/unions? What are you talking about? You don't need multiple return. You can use a struct and it's the same thing.
One of the small but important significances of Rust is that it very often gets to have the same machine code as a correct "in-band error signalling" strategy from C but with source code that the maintainers can actually understand.
And really often when your "in-band error signalling" in Rust is more expensive you realise (perhaps to your horror) that your C wouldn't be correct, so you just dodged a bullet. For example Option<OwnedFd> is, like OwnedFd, a 32-bit value, Unix has always reserved -1 to mean invalid, so Rust can treat that as a niche. But the Windows equivalent Option<OwnedHandle> can't do this because, well, cue Raymond Chen: https://devblogs.microsoft.com/oldnewthing/20040302-00/?p=40...
The first 2 it has, and the 3rd, you really don't want.
For the other part of the issue (the truncation in SHA512), in Rust you could've had:
Now the truncation is a terrible idea in the first place, but at least with this it would have been entirely obvious to the caller that it was there.
I would be more concerned about the lack of explicit return types, one of the arguments for strongly typed languages is that you should not have ambiguous data and yet…
Granted I mostly work with high level programming languages so I may be missing something.
You must be new here. While I applauded the idea of musl when it first came out (coincidentally, glibc wasn't having the best time in its development then), the developer's arguments why <some behavior drastically different from every libc under the sun> was akchyually correct, which was why you had to fix a program that hadn't been broken for 30 years and now suddenly was, made me put him under the "clowns" category and never look at musl seriously again.
When later it turned out that musl's procrustian stack size made Python not really runnable under it, it cemented my resolve to not go near musl.
And now we have this.
I’m also reminded of the clowns pushing “it’s smaller!” container images based on social media vibes rather than analysis where, yes, not using Debian+glibc saved tens of megabytes on the base OS but did so at the expense of measurable performance reductions & compatibility issues like the one you mentioned, and literally every single one of those dudes I worked with was shipping containers pushing a gigabyte so the size reduction had no measurable impact on deployments.
OK, I think I see what’s going on with this, in this configuration.
The goal from an attacker’s perspective is to get this to be true: `$ret = crypt($pw, $hash); $ret == $hash` when called by OpenSSH’s sshd. This is how sshd validates that the user logging in knew the account password.
The `$hash` is the “settings” to the crypt call and will normally look like “$6$--gibberish” for users with passwords set, but could look like “*” or “!” for users not intended to be able to login.
The bug is from the intersection of all of these things:
1. musl can return “*” for errors, rather than leave the return value NULL. Other libc have adopted something like this too, but seem to use a different result “*0”.
2. musl can also return “+” for errors, but only does so if $hash starts with “*”. This is intended to eliminate the possibility of an error causing `$ret == $hash` to be true, however it assumes that applications calling `crypt()` will set $pw and $hash to values corresponding to the `$ret == $hash` comparison to be made immediately afterwards.
3. OpenSSH can be convinced to pass the hash of a different user if the hash is “*” or “!” to avoid timing attacks that can enumerate the user list, so it will set $pw and $hash to correspond to different users. $hash will be a real “$6$--gibberish” style hash in this case, and OpenSSH expects `crypt()` to either return NULL or return a hash string. But now there’s two hashes OpenSSH uses. It does: `$ret = crypt($pw, $hash2); $ret == $hash1`;
4. This should normally not be a problem because OpenSSH will pass in valid $pw and $hash2 that should not lead to errors in hashing, so the $ret that musl generates should be a real hash that cannot match the “*” or “!” $hash1 for the login-disabled user. However as a DDoS mitigation, musl will return error if the password is too long when using SHA-2-based hashes (the default, it seems).
5. This error will result in a non-NULL result of “*” or “+”. Since OpenSSH passed in a real hash ($hash2), musl will return “*”, which compares equal to the actual user hash $hash1 for the disabled-login user.
The OpenSSL adjustment ensures a minimum hash length for the user before logging them in, even if crypt() succeeds somehow.
This is a vastly clearer explanation than the linked page. Thank you!
Because Claude wrote the linked page. Claude is impressively bad at communicating these days. with gpt-5.6+ approaching Claude level like 30% of time and Gemini much clearer but also the most annoying 7 year old ever, it’s a pretty lame environment especially for people who r new to everything
Fun!
I was able to reproduce this on Alpine 3.23.7 with OpenSSH_10.2p1.
Luckily PermitRootLogin [0] hasn't allowed logins with passwords for root since 2015 [1]. I'm guessing that's at least part of why this went undiscovered for so long.
0: https://man.openbsd.org/sshd_config#PermitRootLogin
1: https://cvsweb.openbsd.org/diff/src/usr.bin/ssh/sshd_config?...
Did anyone get it to work? I tried on the official alpine docker image, enabled password login for root. The shadow entry has ! as password by default, this didn't work with a > 256 character password (i also did passwd -l which also does !). I manually changed it to * and it still didn't work.
Am I doing anything wrong here?
OpenSSH_10.3p1, OpenSSL 3.5.9 29 Sep 2026
PRETTY_NAME="Alpine Linux v3.24"
Nope, wasn’t able to reproduced it in my firecracker VM, which isn’t publicly accessible anyway.
Did you try one incorrect standard password fail first?
As far as I understand, it wont work on default setups. You need musl-c, no pam and openssh.
In Alpine, these would all be the case for an out of the box install with openssh added unless you specifically install openssh-server-pam and configure sshd_config to use PAM (Alpine is already musl-c based and doesn't default to PAM).
Doesn't it also need a user to be added with a password entry?
I only ever see Alpine Linux used for containers which don't need accounts with interactive user logins, which is not to say it doesn't exist, just that it doesn't seem like Alpine comes with all preconditions met out of the box
EDIT: works after downgrading OpenSSH, turns out even EOL Alpine version got updated packages!
Also didn't have much luck on Alpine 3.20.10 with OpenSSH_9.7p1 which I've freshly installed from an official ISO.
Last two entries in /etc/shadow:
SSHing into test@ with one 'wrong' password then one 'long' password doesn't work. I have UsePAM no and PasswordAuthentication yes in my sshd_config.
No, didn't work for me open OpenWRT x64 running in a container but that is probably 'cause I'm using dropbear instead of openssh-server. That's what OpenWRT uses by default so the impact there will be minimal assuming that most installations don't change to openssh-server - it isn't installed by default.
It's because alpine has updated all openssh-server packages already. Even from EOL alpine versions.
oooh, that'll do it.
Didn't notice that the openssh-server-10.3_p1-r2 was released today.
Ahh! Wasn't working on 3.16, which does indeed have an updated package.
But, got it to work on 3.15 - which requires changing the ! to a * in the shadow file in addition to other steps (making another user with a hash, setting PermitRootLogin to yes, etc.).
https://pkgs.alpinelinux.org/package/v3.16/main/x86_64/opens... Build time 2026-11-05 06:53:46
https://gist.github.com/markuman/acd2c2e7e08c849cfafe9e47bec...
on 3.21 with the previous version ...
I can't reproduce it either. I used alpine:3.24.1 and openssh is openssh-server-10.3_p1-r2
I tried adding PermitRootLogin yes and PasswordAuthentication yes. Tried adding another user with a valid password.
Verified shadow entry has a *. Can't login as root or a test user. Tried another incorrect password first as well.
edit: can reproduce after `git revert 384e25e6bd1f2e7b30095900e48b570d46953510` in aports and rebuilding openssh without the fix. It also accepts the password on the 2nd+ attempt, NOT the first.
Offtopic: this is a very cool way to present commits and code excerpts. Love classic Windows styling.
Were those pictures with links generated using a publicly available tool that we could use, or were it custom (vibe)coded specifically to create this page?
This looks entirely vibe-coded to me. No one is going to put so much effort for a vuln.
For OpenWRT, AsusWRT etc, I believe they use dropbear ssh by default instead of OpenSSH, which apparently isn't affected?
Yes, correct for OpenWrt. OpenWrt defaults to dropbear for both server and client. However, more advanced users may optionally choose to replace it with OpenSSH, or install OpenSSH side-by-side, to gain additional features of OpenSSH.
Dropbear added the 100 character password limit in 2019.77, so earlier versions might be susceptible.
I'm starting to realize that trusting some random people who wrote the gruddiest, boringest, most torturous low-level stuff might have been a bad plan.
At this point I feel embarrassed in front of the AIs.
That's a well-made site, yet I feel nothing.
LLM output fatigue?
I didn't hate the writing even if it's AI, but I deeply disliked the animations. I don't know if that's LLM fatigue or not.
Apple sideways traffic light fatigue.
Good to know I'm not the only one annoyed by that superfluous piece of ${whatever} signalling.
What is dead can never die. All blueteamers are ironborn these days.
Maybe that's on you though. I enjoyed it, though the discrepancy between the `*sshole` name and the `sshhole.com` domain made me twitch. How is anyone[0] obsessive enough to find this and write it up and yet not obsessive enough to make the amount of `h` consistent?
[0]: Be they human or LLM. Or an entity with any proportion of the two. I do not judge nor discriminate.
Look closely. The second h is behind the word and almost as dark as the background
Oh. Thank you!
I thought it was a great write up. It did feel a bit AI-coded, but whether it actually was or not, it's still a good bit of work imo.
I dunno, there were some strange discrepancies in the explanation (and captions). Didn't really hang together.
It would be weird to spend this much effort doing the site by hand, for a bug that the author says was found by a swarm of agents.
Looks good overall, but I was wondering if eg. "the timer learns nothing" and "no X, no Y, no Z" was slop rather than a deliberate choice.
Wow. I wonder which of the common fuzzers would have found this a decade ago. If literally any password over 256 chars works, that means nobody has ever fuzzed openssh on musl linux
The last few weeks have made me feel very good about my policy of zero internet-accessible ssh ports, ever. On AWS, use SSM. For a VPS or home server, access everything over WireGuard.
What is out there that uses musl without PAM and hosts an OpenSSH SSHd with PasswordAuthentication?
As in: "Actually out there"
The hypothetical Alpine exists, yes, but what runs that like that?
A large number of Docker containers?
Edit: Sure, a small minority presumably run sshd under these conditions. But a small minority times the number of Alpine containers running in the world gets to a large absolute number.
Edit 2: You really don't need to look very hard to find public container examples at million-download scale.
Docker containers that run sshds?
Many, many Docker containers rely on "docker exec" or the kubectl equivalent to gain CLI access when needed. To have sshd in an Alpine Docker container, you're generally need to be running init and a bunch of demons, not just a single standalone service.
I'm guessing in practice relatively few people are actually exposed. But if they are, it's catastrophic.
Docker containers run sshd?
What is out there that uses musl without PAM and hosts an OpenSSH SSHd with PasswordAuthentication?
Possibly public SFTP servers. I have allowed null passwords in the past for anonymous public SFTP and I run Alpine Linux exclusively for my servers both VM's and physical. The shadow package (PAM) did not get installed by default. I installed it but I had to specify it in the installation so there are likely people without it. There is probably a way to find them on shodan.io.
I will activate one for people to play around with for today:
There's no firewall and no password. Hack away HN.
cd /pub
get so*
Agent sandboxes today probably
Reminds one of https://www.openssh.org/txt/buffer.adv.
It's amazing how similar this exploit payload is to the 20+ year-old Quake 3 vulnerabilities found by Luigi Auriemma (aluigi), which also used the exact same 256-to-1024 character range and nothing more than a long string of AAAA.... Here you're feeding >256 A's up to a 1024-byte limit to trip musl's defensive length cap, whereas back in the mid-2000s, Luigi was famous for publishing one-line .cfg scripts where the entire exploit was literally "say aaaaa..." repeated a few hundred times overflowing server's memory.¹ ²
A great example is Jedi Academy, a 2003 Quake 3 engine game whose multiplayer is still actively played today (its open-source engine port, openjk, is even in the Debian repos btw). Luigi had two classic scripts for it on his site: Jedi Academy <= 1.011 in-game server buffer-overflow (jamsgbof)¹, which crashed the server just by pushing a string of as past the 1024-byte console buffer, and Quake 3 engine in-game players kicking (q3msgboom)², where a wall of as hit the engine's 1022-char truncation limit and the leftover bytes confused the parser into disconnecting everyone on the server.
Kind of wild that 20 years later, the exact same payload goes from crashing Quake 3 matches from the tilde console to getting root on some SSH servers.
[1] https://web.archive.org/web/20101227181948/http://aluigi.alt... [2] https://web.archive.org/web/20060522175643/http://aluigi.alt...
Wait so musl, famously a stickler for standards, just changed the behaviour of a POSIX function?
From the other thread’s source [1], it affects musl without PAM. You can set PasswordAuthentication=no or update to remediate.
[1] https://hachyderm.io/@damienmiller/117563026759098135
Why is this not yet published on the official website and why is there no CVE? https://www.openssh.org/security.html
[delayed]
To be fair, I have less than zero sympathy for anyone who runs SSH on any platform without `PasswordAuthentication=no` in 2026.
Its not asking for trouble, it is there will be trouble, not if but when.
As for the people who say "well, I run SSH on port 942329053052". Well guess what, the bots make short work on that. We tried it at $work as an experiment, multiple bots found it in less than a couple of hours. That's why your SSH config must be hardened, preferably running on a hardened OS too.
This particular bug works even with password authentication turned off.
> This particular bug works even with password authentication turned off.
Does it ?
Somebody here has already said "You can set PasswordAuthentication=no or update to remediate"
We don't use musl at $work anyway, so I've no means to test.
Where did you get that idea? The entire bug is about password hashing. With password auth off, that's not even attempted.
The exploit works for a user account that has no password. This is often confused with turning off password auth, especially in containers that have only one usable account.
It's not just the parent commenter. I'm sure somebody out there is going to remove their account password instead of editing their sshd_config in an attempt to "patch" this vulnerability, actually exacerbating the problem.
Bug > are password logins still on? they are by default
You > This particular bug works even with password authentication turned off.
No. The bug is related to password authentication. If you do not have password authentication then you are not affected.
What freaks some people out is they chose parameters where they do have password authentication but they expect to always fail. That's a bad choice, like OK you did fit a cheap manual keyhole, but you threw the keys away thinking now nobody can open that - you realise somebody with a cheap jiggler can open it right ?
read the article again
100% and with local tool calls many AI systems will do ssh "for you" and end run around any security theatre that you may have going on with LLMs.
How is password auth weaker than key auth? Bugs in auth code can happen in both pathways. And apart from stupidly short passwords both should be equally impossible to brute-force.
In other words, conceptually, at the end if the day, isn’t a key just another name for a password, really?
What people think of as a very strong password often has <100 "security bits" of entropy.
Keys are usually at least 128 bits of entropy, and it's easy to take them up to 256.
Yes, both are a shared secret, but password auth - even with challenge-response - is weaker than key auth exactly because key auth provides more guess resistance.
2^100 is a lot of things to try though
Especially if you have Fail2Ban set up.
Fail2Ban is kind of required unless one like running out of sockets and are unburden by high cpu and disk load.
Huh? I run ssh (OpenSSH) on port 22 with root login enabled and no fail2ban on a single-core laptop cpu from fifteen years ago. The load average is 0.00 even with the small mail and web server that runs on it
What cpu and especially what disk load are you talking about? Also not running out of sockets, not sure if that's RAM-dependent (the box has 2GB)
> if you have Fail2Ban set up.
Worth noting that if you are running a remotely recent version of SSH it has everything you need built-in. No need for Fail2Ban on SSH these days if your config is fully modernised.
But the SSH keys are based on asymmetric crypto, not shared secrets.
> What people think of as a very strong password often has <100 "security bits" of entropy.
The best password in the world will still be defeated by a simple keylogger or breach of your password manager.
Password gets sent to the server. Private key does not get sent to the server, and authentication protocol can be forwarded safely, enabling things like ssh-agent, FIDO SSH keys. This is solvable with passwords (see: augmented PAKE), but `PasswordAuthentication` isn’t that. But there are also settings where none of this really matters, yes, to be fair if that’s what you’re referring to.
SSH certificates are cool too.
password doesn’t get sent to the server, hash does.
but I guess that the hash is always the same unlike with pub priv key mechanism.
> password doesn’t get sent to the server, hash does.
Kind of irrelevant what gets sent to the server and what happens on the server.
Password is already easily defeatable long before it even leaves your computer, thanks to keyloggers and/or password manager breaches and/or old-school shoulder surfing (assisted in the 2026 era by covert filming and AI).
All of which are not vulnerabilities with hardware-backed keys which you don't even need a Yubikey for these days since most modern computers and smartphones have secure enclaves and/or TPMs. (Yubikeys are still great though).
No, you are wrong. The password gets sent to the server. That said, I still enable passwords on servers, but don't ever share passwords between trust domains.
Password reuse is the problem. The password hash is stolen from some other site and brute forced offline.
Same issue with key reuse. Unless you have a policy to rotate them and verify which host they login from, someone's unencrypted hard drive from 5 years ago is more likely to have a key than password.
> someone's unencrypted hard drive from 5 years ago is more likely to have a key than password.
Even 5+ years ago, hardware-backed SSH keys were a thing (Yubikey). The only difference today is that its 100% easier to do keys properly because of the widespread commoditisation of secure enclaves in desktops and smartphones to support FIDO, its basically free of charge now because you're not obliged to buy a Yubikey.
you claimed my favorite game's character name!
I run SSH with password authentication on but the port binds to a ULA address. It’s fine. No need to be so absolutist.
> No need to be so absolutist.
Why not ?
Even if you don't want to go all the way to SSH certificates, SSH public-key authentication is laughably easy to do.
I also don't buy the argument "but its on a ULA address". Attacker's old favourite these days is finding a way in (North–South) and then using that as a stepping stone (East–West). Also the general concept of "lower security is OK because its on the LAN" is so 1997.
Yeah because if attackers are already finding a way in, they can easily read my ~/.ssh/id_ed25519. A password is strictly better, although not by much because lateral movement is very easy anyways. The only exception is if the private key is actually on a HSM, which is the case for all my SSH private keys on iOS.
> read my ~/.ssh/id_ed25519.
No excuse for doing that these days.
You can use a Yubikey or you can use your computer's secure enclave or TPM with FIDO at no extra cost.
A password is never, ever "strictly better". Seriously, you're just making shit up now.
> Its not asking for trouble, it is there will be trouble, not if but when.
Did any of those bots brute force a password? Because a 20 character random password is comparable in brute force complexity to an SSH key. The experiment you ran was just as valid for SSH keys on that port, and had no bearing on password vs key.
> Did any of those bots brute force a password?
The point is they found the security by obscurity so-called "hidden" port in less than a couple of hours.
At that point, what they did is irrelevant. The point is that security by obscurity does not work in 2026.
> Because a 20 character random password is comparable in brute force complexity to an SSH key.
You can't be serious with your comment.
No its not.
And even then, SSH key is asymmetric, you're not sending the private key to the server. But with a password you are, which leaves you vulnerable to many attack vectors that simply do not exist with keys.
> The point is that security by obscurity does not work in 2026.
I feel the opposite, note how most all AI vulns discovered use source code level analysis, empirically keeping source code hidden is more secure.
kerchoff’s principle is misconstrued by a voyeuristic internet that wants to see source code
This is a sampling error - we're only hearing about the public disclosures.
(almost) No company actually has secret source code, only source code not publicly viewable. And the LLMs crawling those don't belong to people who make public disclosures.
Other points are fine, but why do you say a 20-character random password isn’t comparable in brute force complexity to an SSH key?
> > Because a 20 character random password is comparable in brute force complexity to an SSH key.
> You can't be serious with your comment. \n\n No its not.
If you differ in opinion, maybe provide evidence? Especially for a claim like long randomly generated value 1 being absurdly ("can't be serious"-level) weak as compared to long randomly generated value 2
If you mean it's log(62^20,2)≈119 bits of entropy instead of 128+ and so it's theoretically weaker when we build a Dyson sphere around the sun to brute force that key (after somehow obtaining the shadow file, since an online attack would be way too slow), then sure
PSA for OpenWrt users: If you are getting the post quantum message on login which points to openssh.com, you are likely using dropbear nonetheless. Check in System->Software. I was confused and worried why I seemingly had the vulnerable OpenSSH installed, but its just dropbear using an OpenSSH link.
So AFAIU, you are fine.
Did we declare "break the world Thursday" and nobody told me? I feel like it's three weeks in a row that we've had a once-in-a-decade security issue pop up.
I think we should get used to eternal "break the world Thursday", just like our predecessors had to come to terms with Eternal September [0].
[0] https://en.wikipedia.org/wiki/Eternal_September
Thanks you to the team that found this. Exceptionally well explained and funny at the same time. What is most important is how people just checking stuff( remember the .xz hack that was tried?) has save the internets ass so many times. We should give good security researchers UBI for life for just doing good work.
The bugs and commits that "fix" them reveal somewhat of a shitshow for how musl is managed. All projects have bugs, but I can't help but question why the wheel was reinvented here. Many toes have been stubbed along the way.
I avoided using alpine-based containers ever since finding out a lot of Linux server software is actually Linux + SystemD software. The union set API of both Linux and SystemD seems to be the default "Linux API" today.
I use alpine-based containers whenever I can just to keep the world safer from SystemD rotting Linux.
Never enabled sshd there... except on my PostmarketOS PineBook Pro... oh shit!
What is the argument against systemd?
Is it mainly that it is too big?
I feel like everybody still loves the unix philosophy, but the previous tools were too bad, systemd just filled user demand for easier tools.
The moment someone makes a pid 1 software that is good and still modular, open and pluggable I think that will be an instant success.
but alpine famously does not use systemd but openrc?
That's their point. The software they want to use often assumes its being run on a platform with systemd, so running that software on Alpine which makes a point to not use systemd causes challenges for them compared to using a different distro.
This is a super duper annoying site for people who just want to know if their systems are vulnerable, after patching like a dozen critical vulnerabilities in other software over the last week and are almost at the breaking point of resigning.
Can we have a “don’t treat me like five/toddler” / “idgaf about the explanation” quick link to a section for adults who need to patch systems?
(And if your reaction is “just scroll down, stupid”, I’m happy to report that with the scroll jacking, I scroll not enough / past the critical sections nine out of ten times.)
Edit: You may want to read https://sshhole.com/#exposure.
Thanks for mentioning that before I tried to scroll down. Forewarned, I was able to click on the "2026" link once the left-handed "scrollbar" (not the right word but I can't figure out what the right word should be) appeared, which let me jump past most of the verbiage and get to the "are you affected?" section just a couple pages later.
It's people like you I fire with glee
So, nobody fuzz tested sshd before?!?!
Yeah, I am mystified as to how this could have happened.
A+ name
A* name
A{256,} name
*
This is fine :)
Not the worst site, but it's clearly a publicity machine from wakefield.co, whom I haven't heard of. Also, exploitation conditions are super narrow, albeit, any password is wild.
I would like to read this but the scrolling is completely broken on iPad Safari
Magic characters are awesome.
> except a lot of programs never check for NULL. they just compare whatever crypt() gives back with the stored field, hit the NULL, and crash
> so musl (the libc under alpine) goes ok fine, crypt() just won't return NULL anymore. if it fails, it returns a single character instead.
Considering it's been accepted that crashing if malloc returns a NULL is your fault, did musl really feel the need to accommodate bad implementations like this or is this just AI speculation?
> did musl really feel the need to accommodate bad implementations like this
I don't know about this specific case but in general? Yes, totally. No one is going to fix all existing software that depends on libs behaving exactly as glibc, you have to accept some trade-offs. Either your new implementation stops being perfectly simple and clean, or no one uses it.
it's not "glibc behavior", returning null on error is in the spec
See also: Hyrum's Law
"unfortunately, a large portion of programs which call crypt are not prepared for its failure and do not check that the return value is non-null before using it. thus, always "succeeding" but giving an unmatchable hash is reportedly a better behavior than failing on error." [1]
[1] https://git.musl-libc.org/cgit/musl/commit/?id=b3c4cc121f70f...
Such a questionable decision! "Rather than let a bug in a caller (not handling the valid null output and thus crashing) surface, let's just silence it and pretend that the caller is correct! A potential clash in some situations (resulting in this vulnerability) is better than a crash!"
Maybe I should update my plea to fail loudly (https://alejo.ch/3gk) to list this as an example.
It's always a people problem. Doing a bad patch on my side is easier than bothering anyone else to fix their code
> how did I ran into it? [...] i had agent swarms. a lot of them. let's not get into it
Can we please now normalize AI usage in development? Just some other day people asked for "NO AI used" badges for software as measure for quality, and praised i.e. NetBSD for being AI-free. Yes, we come from a phase of AI slop, but it has become obvious that there are plenty of legit usecases where AI beats human-only effort nowadays.
Not sure why but a lot of people seem to be missing that you don't have to look at AI as a binary "you're either with us or you're with the terrorists."
Just do HITL (human in the loop). Use an LLM to help you author, but steer the AI in whatever direction you want. It's like having a slightly delusional copy of yourself to pair program with. If you take the time to provide an LLM with some additional skills files and the like, with you in the pilot seat, you can get solid results (it doesn't look as cool as a hands free agent setup but the quality far surpasses anything they can do solo).
There's a decent-size "any AI usage is theft" contingent that reacts dramatically to any usage of AI whatsoever.
You've got a great point. But let's also acknowledge that there's a pretty stark contrast between these:
- I found a way to get AI to help me while I made this
- I asked AI to make this
The people you're objecting to are complaining about the latter, this is an example of the former.
> Can we please now normalize AI usage in development?
1. It is already normalized outside of a tiny, but very vocal bubble that lives mostly on Bluesky (sometimes also on Reddit/HN/Mastodon).
2. I don't think that even the most staunch AI hater would object to using AI for security research as long as all the artifacts (code, docs) that were produced based on the research are human-written. "Yes, there is a bug in my program, but I refuse to fix it, because I know that you found it using AI" would be a pretty weird position. Not sure, how would you defend it.
That's kind of shocking. I guess the swarm of AI related vulnerability findings continues.
It's shocking that it took so long with the amount of investment and hype you'd expect this kind of bugs to be already fixed, but it still need a human to tell the agents what to do, which could also work with any fuzzing framework
Can we just have a site with the text and images without the awkward scrolling crap? Hijacking basic features is an instant click away from sites for me
Edit: It seems to work fine on mobile. I'm not sure why the scrolling behaviour was added on the desktop version of the site
Of all the named vulnerabilities, I appreciate the history lesson and screenshots of how it got there
The real name of this is sshole - the is the "star" of the show, after all.
*sshole, the * is the star of the show
You can use \ to escape formatting.
This is bottom-up branding I can get behind. ()*()
came for the name, stayed for the story
Haha insane, great find and write up
I really like creativity in the name, the way website built and the content
"tl;dr" was a bit of a downgrade though, but that's fine
it's a nice way to promote the company behind it
I just created an Alpine container, did "apk add openssh" and this doesn't work for me. I assume it's been updated already.
what’s the moral of the story?
alpine stocks are crashing?
musl stocks are crashing?
glibc stonks are up
alternative implementations in general slightly down
does this have CVE or something?
I liked that this site explained the vulnerability in an easy-to-understand way.
I can't understand it. All this scrolling and pictures are distracting me, can't concentrate really.
I think it varies from person to person. Since I'm kind of from the TikTok generation, I don't have much trouble reading this kind of animation, but some people prefer static sites. That's just how it is.
I also found scroll-triggered animations hard to read at first, but these days a lot of sites use them, so I've gotten used to them.
Yep, scrolling through my phone and reading slowly to understand. I'm seeing distracting animations below what I'm reading. And when I go to them, there is no way to restart them. So it completely misses the point.
Related discussion: [0]
[0] https://news.ycombinator.com/item?id=50377221
One more reason to build your (own) Docker images on 'FROM scratch' (basically nothing).
No, the Alpine containers don't come with sshd preinstalled. You'd have to manually install via dockerfile and leave it unconfigured.
No one runs sshd in containers, at least I hope so. What would even be the point when you have docker/kubectl commands available?
at this point my only reaction is "are you fucking kidding me"
Yet another clankered finding creating a clankered website with clankered explanations. To be fair, this one's a lot better than the other clankered equivalents, but I wonder whether these people even know enough about their bug to have their own write-up?
Also, what's with this damn trend of typing in lowercase only? Why is this a thing?
> oh did i say "i"? sorry. i had agent swarms. a lot of them. let's not get into it
Still a cool finding... it's just the communication is becoming a lot worse these days - I want to understand the findings please, not be impressed by your webpage! Biggest gripe in recent memory is https://github.com/xoreaxeaxeax/skitter-creek-bath-salts
> Also, what's with this damn trend of typing in lowercase only?
Anticapitalism.
Anticapitalism that uses an army of clankers?
You made my morning. Got a new dad joke.
you could make a strong case for that!!!
sigh, it's not a new trend. it's just yet another pop-cultural appropriation from the gay community, now mainstream thanks to ai. as trump's gay dementia progresses, pretty soon even he will be truthing about other men's asses in lowercase, just to get a rise out of them!!! however, the *sshole project's shibboleths of lowercasing and anal asterisk punctuation strongly suggest its authors may be bona fide members of the lgbtq+ community.
why do gay people love typing in lowercase?
https://thetastefultwink.substack.com/p/the-queer-lowercase
> Let’s sit and twink about the data. 24.6% of my 19,000+ respondents abandoned capitalization entirely. If you control for age, queer people were 1.5x more likely than straight people to type in lowercase. Lesbians out-lowercased every other sexuality at 28.3%, followed by bisexuals at 24.9%. Honorable mention to the lowercase enbies, at 29.2%.
New and Changing Social Evaluations of All-lowercase and Exclamation Points
https://repository.upenn.edu/server/api/core/bitstreams/edbc...
> both exclamation points and lowercase usage are associated with queer identity.