May 4, 2026
Root, reboot, and comment-war chaos
CVE-2026-31431: Copy Fail vs. rootless containers
Hack scares users, but rootless containers mostly keep the damage boxed in
TLDR: The test showed this exploit can gain admin-like power inside a rootless container, but not easily break out and own the whole host. Commenters were split between relieved and deeply unimpressed, with some demanding faster summaries and others warning the danger is still very real.
A scary new Linux bug nicknamed “Copy Fail” had the comments section doing what comments sections do best: panicking, nitpicking, and dunking on everyone at once. The blog post itself is a careful lab report — the author unpacked the exploit, checked the mystery payload before running it, and showed that inside a rootless container the attack can turn you into “root” only inside that box, not on the host machine. In plain English: the burglar gets the costume, not the master keys.
But the crowd was not in a calm, measured mood. One of the loudest reactions was basically, “Great writeup, but where’s the top-line summary? We’re busy patching and rebooting everything!” That set the tone: readers wanted the emergency version first, the forensics later. Others got sidetracked by the delightfully weird phrase “ELF golfing,” with a mini collective “today I learned” over the exploit author slimming down a tiny program so much that normal tools barely recognized it.
The real drama came from the split between “this is contained, relax” and “absolutely do not relax.” One camp said the result is reassuring: rootless containers did their job and blocked a full machine takeover. The other camp, led by a very grim “Sigh”, warned that the dangerous trick still worked and could still poison shared software in memory. Translation: the house may not burn down, but people are arguing over whether the kitchen is already on fire. And yes, that argument is the actual show.
Key Points
- •The article documents a lab-based investigation of CVE-2026-31431 (“Copy Fail”) to test exploit behavior in a rootless Podman environment.
- •The public exploit’s embedded payload is stored as a zlib-compressed, hex-encoded blob that can be extracted with a short Python script.
- •After decompression, the payload is identified as a statically linked 64-bit x86-64 ELF executable rather than raw shellcode.
- •The exploit is described as overwriting the beginning of /usr/bin/su so the operating system executes corrupted page-cache content instead of the original utility.
- •Forced disassembly shows the payload contains a setuid(0) syscall followed by logic to invoke execve("/bin/sh"), indicating privilege escalation and shell execution intent.