A local privilege escalation vulnerability exists in snap-confine, a set-capabilities core component used internally by Canonical snapd to construct the secure execution environment for snap applications. This vulnerability uniquely affects versions of snap-confine configured with set-capabilities (rather than standard set-uid-root installations). Due to a flaw in how privilege boundaries or security sandboxes are initialized when the binary runs under limited ambient capabilities, a local, unprivileged attacker can exploit this behavior to bypass intended restrictions and execute arbitrary code. Successful exploitation allows the local user to elevate their privileges to full root authority.

On 2026-03-17 13:58:17, Michal Zalewski wrote: Nice work... flashbacks from 2002 (https://lcamtuf.coredump.cx/tmppaper.txt). It's frankly somewhat mind-boggling that distros keep a world-writable /tmp this day and age. Whatever questionable benefits it has, it also contributed to plenty of pointless and easily avoidable vulns. It's required by POSIX which, funny enough, forbids /tmp from being used the way snap-confine is using it. I wouldn't expect either of these projects to care about POSIX, but the same description was copied & pasted into the FHS. And to its credit, systemd has a page full of documentation on how to avoid this exact problem.

1. https://pubs.opengroup.org/onlinepubs/9799919799/basedefs/V1chap10.html 2. https://refspecs.linuxfoundation.org/FHS3.0/fhs/ch03s18.html 3. https://systemd.io/TEMPORARYDIRECTORIES/