medium4.7
CVE-2026-112939
filelock: SoftFileLock removes a live holder's marker when another user forges the PID in a writable marker
Impact
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 packages
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| pip | filelock | >= 3.22.0, <= 4.2.0 | 4.2.1 |
Affected products
| Vendor | Product | Affected versions |
|---|---|---|
| Tox-Dev | Filelock | from 3.22.0 before 4.2.1 |
Weakness classification
References
- NVD record
- CVE.org record
- GitHub advisory
- https://github.com/advisories/GHSA-rfpc-qcw5-3pc4
- https://github.com/tox-dev/filelock/security/advisories/GHSA-rfpc-qcw5-3pc4
- https://nvd.nist.gov/vuln/detail/CVE-2026-112939
- https://github.com/tox-dev/filelock/pull/836
- https://github.com/tox-dev/filelock/commit/eeceaa846cbe4df72718d94c8371ca1ab8f5b3cc
- https://github.com/tox-dev/filelock/releases/tag/4.2.1