CVE-2026-112939

Name	CVE-2026-112939
Description	filelock is a platform-independent file lock for Python. From 3.22.0 until 4.2.1, SoftFileLock can trust a forged process identifier in a marker that an attacker can modify but cannot remove, allowing an authorized contender such as another process of the holder's account or root to act as a confused deputy, remove the live marker, and admit another holder. This issue is fixed in version 4.2.1.
Source	CVE (at NVD; CERT, ENISA, LWN, oss-sec, fulldisc, Debian ELTS, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)
Debian Bugs	1151686

Vulnerable and fixed packages

The table below lists information on source packages.

Source Package	Release	Version	Status
python-filelock (PTS)	bookworm	3.9.0-1+deb12u1	vulnerable
	trixie	3.18.0-1+deb13u1	vulnerable
	forky, sid	4.2.8-1	fixed

The information below is based on the following data on fixed versions.

Package	Type	Release	Fixed Version	Urgency	Origin	Debian Bugs
python-filelock	source	(unstable)	4.2.8-1			1151686

Notes

https://github.com/tox-dev/filelock/security/advisories/GHSA-rfpc-qcw5-3pc4
https://github.com/tox-dev/filelock/pull/836
Fixed by: https://github.com/tox-dev/filelock/commit/eeceaa846cbe4df72718d94c8371ca1ab8f5b3cc (4.2.1)