Comment by justonenote
8 hours ago
Whatever about the specifics of this bug and whether its a useful vector, this is not surprising even in the slightest?
My current opinion on LLMs is that they are superhuman in that they lack fatigue, they have close to full knowledge across all subjects which are known to humans at least publicly, and the fact that you can vibe code a harness to look for bugs in a famously complicated C codebase is intern level stuff and hardly news.
Smart aspiring blackhats will be targeting tmux next, both with light llm jailbreaks, light supply chain attacks (web search results) and LPEs within certain environments which weren't particularly useful before but with agents running on auto mode for hours become a very valuable springboard. I'm not sure on the quality of tmux code but I know its written in C and is very complex and was not at all designed to defend against this type of threat.
Not that it doesn’t have issues, but I’m not sure why you’d choose tmux of all things. It runs as a user and has no privileges to escalate. It was written for and is part of OpenBSD and follows their security hardening practices.
(There actually was one privilege escalation bug in tmux, but it actually seems like a distro packaging error. The distro setgid the executable so the resulting shell inherited the additional group. This didn’t require any exploit, that’s just how child process inheritance works.)
as I mentioned in another sibling, its because it's a very common denominator in high value targets. I didn't know its legacy was from OpenBSD but I really doubt that that helps it much in this scenario, when I say LPE I'm not talking about user to root elevation, I'm talking parsed text/control sequences to arb code execution in the user context. These will slip past llm classifiers as safe and I'm fairly sure that they are extremely common in codebases like tmux, despite them having strong security posture its just a threat that was previously a bit outlandish and not accounted for.
persisted malicious code running in your tmux process that you don't know about is probably not where you want to be, for obvious reasons.
Agent harnesses aren’t going to output ansi escape sequences verbatim to the terminal.
If you wanted to booby trap a repository then you’re far better off with a prompt injection attack.
I don’t think tmux is the most worthwhile target because you’d need the user to either execute code locally (thus negating any point in targeting tmux) or rely on the user curl or cat some compromised document (in which case you’re better off targeting curl or cat).
the point is tmux is being used by many developers working in high value targets to automate long running unsupervised agent tasks. you don't need the user to execute code, you need _their agent_ to stumble on the wrong search result or github repo and it wont be noticed for hours that they loaded a persistent threat into your environment.
That seems even harder to do because an agent wouldnt be output text verbatim, which means you cant make use of a rendering bug (eg parsing escape codes).
So you’re back to depending on the agent to execute code locally. at which point you’ve already compromised the system so don’t need a tmux bug.
I’ve spent a lot of time in tmux. Including writing a frontend for it. So I’m probably more familiar than most. And I hear a lot of people say tmux (specifically) is a vulnerability because it’s written in C. But I struggle to see how it’s any more of a vulnerability than (for example) coreutils. Or any other piece of software for that matter.
the fact that you can vibe code a harness to look for bugs in a famously complicated C codebase is intern level stuff and hardly news
It seems like this would have been pure fantasy not that long ago though. So why isn’t it noteworthy again? I don’t really follow what you’re complaining about.