filelock is a platform-independent file lock for Python. Prior to version 3.20.3, a TOCTOU race condition vulnerability exists in the SoftFileLock implementation of the filelock package. An attacker with local filesystem access and permission to create symlinks can exploit a race condition between the permission validation and file creation to cause lock operations to fail or behave unexpectedly. The vulnerability occurs in the _acquire() method between raise_on_not_writable_file() (permission check) and os.open() (file creation). During this race window, an attacker can create a symlink at the lock file path, potentially causing the lock to operate on an unintended target file or leading to denial of service. This issue has been patched in version 3.20.3.
History

Wed, 14 Jan 2026 00:15:00 +0000

Type Values Removed Values Added
References
Metrics threat_severity

None

threat_severity

Moderate


Mon, 12 Jan 2026 17:15:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Mon, 12 Jan 2026 14:45:00 +0000

Type Values Removed Values Added
First Time appeared Tox-dev
Tox-dev filelock
Vendors & Products Tox-dev
Tox-dev filelock

Sat, 10 Jan 2026 06:15:00 +0000

Type Values Removed Values Added
Description filelock is a platform-independent file lock for Python. Prior to version 3.20.3, a TOCTOU race condition vulnerability exists in the SoftFileLock implementation of the filelock package. An attacker with local filesystem access and permission to create symlinks can exploit a race condition between the permission validation and file creation to cause lock operations to fail or behave unexpectedly. The vulnerability occurs in the _acquire() method between raise_on_not_writable_file() (permission check) and os.open() (file creation). During this race window, an attacker can create a symlink at the lock file path, potentially causing the lock to operate on an unintended target file or leading to denial of service. This issue has been patched in version 3.20.3.
Title filelock Time-of-Check-Time-of-Use (TOCTOU) Symlink Vulnerability in SoftFileLock
Weaknesses CWE-362
CWE-367
CWE-59
References
Metrics cvssV3_1

{'score': 5.3, 'vector': 'CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:H'}


cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published: 2026-01-10T05:59:28.872Z

Updated: 2026-01-12T16:45:50.638Z

Reserved: 2026-01-08T19:23:09.856Z

Link: CVE-2026-22701

cve-icon Vulnrichment

Updated: 2026-01-12T16:45:47.955Z

cve-icon NVD

Status : Awaiting Analysis

Published: 2026-01-10T06:15:52.673

Modified: 2026-01-13T14:03:18.990

Link: CVE-2026-22701

cve-icon Redhat

Severity : Moderate

Publid Date: 2026-01-10T05:59:28Z

Links: CVE-2026-22701 - Bugzilla