CVE-2026-112909

Name	CVE-2026-112909
Description	filelock is a platform-independent file lock for Python. Prior to 4.2.1, UnixFileLock can truncate a regular file renamed onto the lock path when another local user has actual rename permission, or hard-linked there under a permissive hard-link policy; when an explicit mode is requested, affected versions from 3.10.2 can also change that file's mode. 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-69hj-f68j-2879
https://github.com/tox-dev/filelock/pull/835
Fixed by: https://github.com/tox-dev/filelock/commit/e1e825b1992f69fb6b346dc395d5ae4893536c0a (4.2.1)