CVE-2026-112939
filelock: SoftFileLock removes a live holder's marker when another user forges the PID in a writable marker
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.
INFO
Published Date :
Oct. 20, 2026, 3:17 p.m.
Last Modified :
Oct. 21, 2026, 6:02 p.m.
Remotely Exploit :
No
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | |||||
| CVSS 3.1 | MEDIUM | MITRE-CVE | ||||
| CVSS 3.1 | MEDIUM | [email protected] |
Solution
- Update filelock to version 4.2.1.
- Remove or replace the vulnerable filelock package.
- Ensure marker files are protected from unauthorized access.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-112939.
| URL | Resource |
|---|---|
| https://github.com/tox-dev/filelock/commit/eeceaa846cbe4df72718d94c8371ca1ab8f5b3cc | Patch |
| https://github.com/tox-dev/filelock/pull/836 | Patch |
| https://github.com/tox-dev/filelock/releases/tag/4.2.1 | Release Notes |
| https://github.com/tox-dev/filelock/security/advisories/GHSA-rfpc-qcw5-3pc4 | Exploit Mitigation Patch Vendor Advisory |
| https://github.com/tox-dev/filelock/security/advisories/GHSA-rfpc-qcw5-3pc4 | Exploit Mitigation Patch Vendor Advisory |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-112939 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-112939
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-112939 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-112939 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
Initial Analysis by [email protected]
Oct. 21, 2026
Action Type Old Value New Value Added CPE Configuration OR *cpe:2.3:a:tox-dev:filelock:*:*:*:*:*:python:*:* versions from (including) 3.22.0 up to (excluding) 4.2.1 Added Reference Type GitHub, Inc.: https://github.com/tox-dev/filelock/commit/eeceaa846cbe4df72718d94c8371ca1ab8f5b3cc Types: Patch Added Reference Type GitHub, Inc.: https://github.com/tox-dev/filelock/pull/836 Types: Patch Added Reference Type GitHub, Inc.: https://github.com/tox-dev/filelock/releases/tag/4.2.1 Types: Release Notes Added Reference Type CISA-ADP: https://github.com/tox-dev/filelock/security/advisories/GHSA-rfpc-qcw5-3pc4 Types: Exploit, Mitigation, Patch, Vendor Advisory Added Reference Type GitHub, Inc.: https://github.com/tox-dev/filelock/security/advisories/GHSA-rfpc-qcw5-3pc4 Types: Exploit, Mitigation, Patch, Vendor Advisory -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Oct. 20, 2026
Action Type Old Value New Value Added Reference https://github.com/tox-dev/filelock/security/advisories/GHSA-rfpc-qcw5-3pc4 Added SSVC {'id': 'CVE-2026-112939', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'poc'}, {'automatable': 'no'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-10-20T15:14:32.481979Z'} -
New CVE Received by [email protected]
Oct. 20, 2026
Action Type Old Value New Value 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. Added CVSS V3.1 AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:N Added CWE CWE-345 Added Affected New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/112xxx/CVE-2026-112939.json">CVE-2026-112939</a> Added Reference https://github.com/tox-dev/filelock/commit/eeceaa846cbe4df72718d94c8371ca1ab8f5b3cc Added Reference https://github.com/tox-dev/filelock/pull/836 Added Reference https://github.com/tox-dev/filelock/releases/tag/4.2.1 Added Reference https://github.com/tox-dev/filelock/security/advisories/GHSA-rfpc-qcw5-3pc4