CVE-2026-112908: Permission Flaw (CVSS 5.3)

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.

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CVSS v3.1 Score

5.3

MEDIUM

CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:L

EPSS — Exploit Prediction

0.0012

Probability of exploitation

0.02%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-732 CWE-732

References

Other References

https://github.com/tox-dev/filelock/commit/8cf51802158b9cf7e1fc560c2da30491a662cfde https://github.com/tox-dev/filelock/commit/bfa066d65a1ba9106f86ee9d027f7588b9c77e03 https://github.com/tox-dev/filelock/pull/839 https://github.com/tox-dev/filelock/releases/tag/4.2.1 https://github.com/tox-dev/filelock/security/advisories/GHSA-6627-m3xw-93mp https://github.com/tox-dev/filelock/security/advisories/GHSA-6627-m3xw-93mp

Frequently Asked Questions

What is CVE-2026-112908? +

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. It has a CVSS v3.1 base score of 5.3 (MEDIUM).

How severe is CVE-2026-112908? +

CVE-2026-112908 has a CVSS v3.1 score of 5.3 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0012, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-112908? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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