CVE-2026-112939

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.

CVSS 3.1

4.7CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:N

EPSS

0.1% chance of exploitation in the next 30 days; higher than 3% of CVEs (scores of 2026-10-25)

CWE

CWE-345

Published

2026-10-20

Modified

2026-10-21

Record from

the NVD, synced 2026-10-22

Affected

• tox-dev:filelock

References

• https://github.com/tox-dev/filelock/commit/eeceaa846cbe4df72718d94c8371ca1ab8f5b3cc
• https://github.com/tox-dev/filelock/pull/836
• https://github.com/tox-dev/filelock/releases/tag/4.2.1
• https://github.com/tox-dev/filelock/security/advisories/GHSA-rfpc-qcw5-3pc4
• https://github.com/tox-dev/filelock/security/advisories/GHSA-rfpc-qcw5-3pc4

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