CVE-2026-112939

filelock: SoftFileLock removes a live holder's marker when another user forges the PID in a writable marker

Published Oct 20, 2026 CVSS 3.1 · 4.7 Medium EPSS < 1% KEV · Not listed
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Github GHSA Github GHSA GHSA-rfpc-qcw5-3pc4 filelock: SoftFileLock removes a live holder's marker when another user forges the PID in a writable marker
History
Type Values Removed Values Added
CPEs cpe:2.3:a:tox-dev:filelock:*:*:*:*:*:python:*:*
Type Values Removed Values Added
First Time appeared Tox-dev
Tox-dev filelock
Vendors & Products Tox-dev
Tox-dev filelock
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'poc', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
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.
Title filelock: SoftFileLock removes a live holder's marker when another user forges the PID in a writable marker
Weaknesses CWE-345
References
Metrics cvssV3_1

{'score': 4.7, 'vector': 'CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:N'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
GitHub_M
Published
Updated
Oct 20, 2026, 3:14 PM
Reserved
Oct 19, 2026, 9:30 PM
Status
Analyzed
Published
Oct 20, 2026, 3:17 PM
Modified
Oct 21, 2026, 6:02 PM
Severity
Moderate
Public date
Oct 20, 2026, 2:38 PM