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.
Affected products
tox-dev: filelock
References5
- github.com/tox-dev/filelock/security/advisories/GHSA-rfpc-qcw5-… ExploitMitigationPatchVendor Advisory
- github.com/tox-dev/filelock/security/advisories/GHSA-rfpc-qcw5-… ExploitMitigationPatchVendor Advisory
- github.com/tox-dev/filelock/commit/eeceaa846cbe4df72718d94c8371… Patch
- github.com/tox-dev/filelock/pull/836 Patch
- github.com/tox-dev/filelock/releases/tag/4.2.1 Release Notes
Metrics
- CVSS 3.1
-
4.7
MEDIUM
Score source: CNA
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:N - EPSS — exploit probability
- 0% percentile: 3 · as of 9 November 2026
- CWE
- CWE-345
Could this be exploited in your environment?
A patch closes the known hole. A penetration test shows what an attacker can still reach — with proof.