Description
filelock is a platform-independent file lock for Python. From version 3.30.0 until version 4.2.1,  StrictSoftFileLock  and  AsyncStrictSoftFileLock  on POSIX systems create coordination and claim directories without applying the caller’s restrictive lock mode. A permissive umask or inherited default ACL can leave these directories writable by another local user, allowing that user to delete an active holder’s claims. Another authorized process can then acquire the lock while the original holder remains in its critical section. An attacker can also plant malformed claims to prevent acquisition. This issue is fixed in version 4.2.1.
Published: 2026-11-05
Score: 5.3 Medium
EPSS: < 1% Very Low
KEV: No
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Remediation

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Tracking

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Advisories
Source ID Title
Github GHSA Github GHSA GHSA-6627-m3xw-93mp filelock: StrictSoftFileLock creates its claim directories without the lock mode, so another local user with a write bit on them can end a live hold
History

Fri, 06 Nov 2026 12:15:00 +0000

Type Values Removed Values Added
Weaknesses CWE-279
References
Metrics threat_severity

None

threat_severity

Moderate


Fri, 06 Nov 2026 00:00:00 +0000

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

Thu, 05 Nov 2026 22:15:00 +0000

Type Values Removed Values Added
Description filelock is a platform-independent file lock for Python. From version 3.30.0 until version 4.2.1,  StrictSoftFileLock  and  AsyncStrictSoftFileLock  on POSIX systems create coordination and claim directories without applying the caller’s restrictive lock mode. A permissive umask or inherited default ACL can leave these directories writable by another local user, allowing that user to delete an active holder’s claims. Another authorized process can then acquire the lock while the original holder remains in its critical section. An attacker can also plant malformed claims to prevent acquisition. This issue is fixed in version 4.2.1.
Title filelock: StrictSoftFileLock creates its claim directories without the lock mode, so another local user with a write bit on them can end a live hold
Weaknesses CWE-732
References
Metrics cvssV3_1

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


Subscriptions

Tox-dev Filelock
cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-11-05T21:54:53.585Z

Reserved: 2026-10-19T20:16:09.857Z

Link: CVE-2026-112908

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-11-05T22:17:46.693

Modified: 2026-11-05T22:17:46.693

Link: CVE-2026-112908

cve-icon Redhat

Severity : Moderate

Publid Date: 2026-11-05T21:54:53Z

Links: CVE-2026-112908 - Bugzilla

cve-icon OpenCVE Enrichment

Updated: 2026-11-06T14:00:07Z

Weaknesses
  • CWE-279

    Incorrect Execution-Assigned Permissions

  • CWE-732

    Incorrect Permission Assignment for Critical Resource