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Copy Fail

copy.fail

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Re: Copy Fail

#201
post #34

Debian page: https://security-tracker.debian.org/tracker/CVE-2026-31431

Oddly, the POC doesn't work on my Debian 12 (Bookworm) EC2 instance. Everything that should indicate it's vulnerable is there, including the ability to socket(38,5,0).bind("aead", "authencesn(hmac(sha256),cbc(aes))")

What kernel version is it? (`uname -r`)

Re: Copy Fail

#202
post #92

For mitigation, the page currently basically just says: > Update your distribution's kernel package to one that includes mainline commit a664bf3d603d But it isn't very clear to me what Kernel version you can expect that to be in. For Arch/CachyOS, the patch seems to be included in 6.18.22+, 6.19.12+ and 7.0+. If you're on any of the lower versions in the same upstream stable series, you're likely vulnerable right now…

On a git repo that has as remotes https://github.com/torvalds/linux.git https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git as remotes: running a search for commit a664bf3d603d's commit message: git log --all --grep 'crypto: algif_aead - Revert to operating out-of-place' '--format=%H' | xargs -I '{}' git tag --contains '{}' | sort -u outputs these tags as having the fix: v6.18.22 v6.18.23 v6.18.24 v6.18.…

Here's the diff if you wanna play in your source (Gentoo, looking at you):

https://github.com/torvalds/linux/commit/a664bf3d603d

6.18.25-gentoo-x86_64 has the patch for Gentoo.

Re: Copy Fail

#203
I wasn't able to unload algif_aead on RHEL 9/10 because it's built in, rather than a module.

So here the next-best thing I found: Disable AF_ALG via systemd. Needs drop-ins for all exposed services. Here an Ansible playbook that covers ssdh and user@, which are the main ones usually.

https://gist.github.com/m3nu/c19269ef4fd6fa53b03eb388f77464d...

Re: Copy Fail

#204

SUID binaries once again assisted a local privilege escalation attack. This is a major problem that distros can't keep ignoring.

There's a claim upthread that a straightforward variation works against /etc/passwd.

Re: Copy Fail

#205
post #40

The page itself seems vibecoded and a bit of an advertisement, but it does look like the vulnerability is real and high risk. It does explain the big security update I just got, guess I'll prioritize updating today.

These guys don't need to advertise, they are already 100% busy with work. But who wastes their time manually creating web pages? Especially kernel devs.

Re: Copy Fail

#206
post #51

So this replaces a SUID binary, in order to run as PID 0. The website claims it can escape "Kubernetes / container clusters" and "CI runners & build farms" but I don't see anything supporting the claim it can escape a container (or specifically, a user namespace). I ran the exploit in rootless Podman, and predictably it doesn't escape the container. They also claim their script "roots every Linux distribution shipped…

It overwrites bytes in memory of any file you can read. It's not hard to imagine how it could escape a lot of things.

Re: Copy Fail

#207

Earlier quoted context omitted.

The page explicitly describes that it is stealthy as it does not make permanent changes, only corrupting the binary in memory.

unfortunately the page can also lie to you haha. it seems people have reviewed the code by now, but running suspicious shellcode you don't fully understand is never a great idea.

I personally had AI review the code, add comments, disassemble the shell code, etc.

Re: Copy Fail

#208
post #140

For agents, if you are concerned about that, block access to "su" as it is interactive anyway. Not loading it into the memory will block the attack. If you are using AgentSH ( https://www.agentsh.org ) you can add a rule to block "su" and soon be able to block AF_ALG sockets if you want to further protect things.

This vulnerability can affect any file you can read. The PoC uses "su" but any setuid binary or any binary that root invokes or is already running as root is vulnerable, as well as many configuration files.

Re: Copy Fail

#209

Yet, some people will still continue to say that "AI" isn't ready to replace (or strongly assist) our workflows, sure, some of the best humans devs left a vulnerability that serious (It's extremely serious, so many container as a service are vulnerable) for 9 years and an agent found it in 1 hour, maybe it's time to wake up and accept that it's UNSAFE to not use AI for security review as well?

A human security researcher found the core issue and an agent searched for where to apply it. I don’t think “an agent found it in one hour” is a fair summary of what happened.

"The starting insight — that splice() hands page-cache pages into the crypto subsystem and that scatterlist page provenance might be an under-explored bug class — came from human research by Taeyang Lee at Xint. From there, Xint Code scaled the audit across the entire crypto/ subsystem in roughly an hour. Copy Fail was the highest-severity finding in the run."

So, if anything, this might argue against the presence of huge quantities of high-severity bugs in this part of the Linux kernel (that could be found by "Xint Code"-class scanning systems).

Re: Copy Fail

#210
post #46

On the downside, I need to push new kernels to all my servers. On this bright side, does this mean Magisk is coming to all unpatched Android phones?

No, Android doesn’t have suid binaries to exploit like in the PoC

The vulnerability can also be used on any binary that is already running as root and you can open for reading. So yes, any android app can now escalate to root if android has the vulnerable module.
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