CVE-2026-112911: filelock — Exploit & Fix

Description

filelock is a platform-independent file lock for Python. From 3.30.0 until 4.2.1, StrictSoftFileLock versions from 3.30.0 and SoftReadWriteLock versions from 4.0.0 can adopt a protocol directory created first by another local user in a shared parent directory, allowing that user to alter protocol state and admit concurrent holders. This issue is fixed in version 4.2.1.

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CVSS v3.1 Score

6.3

MEDIUM

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

EPSS — Exploit Prediction

0.0015

Probability of exploitation

0.04%

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-283 CWE-283

Affected Products

Vendor	Product	Versions
tox-dev	filelock	3.30.0 — 4.2.1

References

Advisories & Patches

https://github.com/tox-dev/filelock/commit/bfa066d65a1ba9106f86ee9d027f7588b9c77e03 https://github.com/tox-dev/filelock/pull/839 https://github.com/tox-dev/filelock/security/advisories/GHSA-9c4x-gm8v-wgc4

Exploits

https://github.com/tox-dev/filelock/security/advisories/GHSA-9c4x-gm8v-wgc4

Other References

https://github.com/tox-dev/filelock/releases/tag/4.2.1

Frequently Asked Questions

What is CVE-2026-112911? +

filelock is a platform-independent file lock for Python. From 3.30.0 until 4.2.1, StrictSoftFileLock versions from 3.30.0 and SoftReadWriteLock versions from 4.0.0 can adopt a protocol directory created first by another local user in a shared parent directory, allowing that user to alter protocol state and admit concurrent holders. This issue is fixed in version 4.2.1. It has a CVSS v3.1 base score of 6.3 (MEDIUM).

How severe is CVE-2026-112911? +

CVE-2026-112911 has a CVSS v3.1 score of 6.3 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0015, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-112911? +

CVE-2026-112911 affects products from tox-dev, specifically: filelock. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-112911? +

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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