What’s Vulnerable › Vulnerabilities

CVE-2026-112914: filelock: SoftFileLock stale-break restore follows a swapped-in symbolic link and hard-links a file of the user running the lock into the lock directory

• Severity: medium (CVSS 5.3 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2026-10-20 · updated 2026-10-21
• Weakness: CWE-363

Description

filelock is a platform-independent file lock for Python. From 4.1.0 until 4.2.1, SoftFileLock can restore a stale marker by name after moving it aside, allowing another local user with rename access in a non-sticky lock directory to swap in a symbolic link and, on a runtime that follows the link and a same-filesystem target, make the lock user hard-link one of its files into the lock directory. This issue is fixed in version 4.2.1.

Affected products

• tox-dev filelock: from 4.1.0 before 4.2.1 — fixed in 4.2.1

How to fix

Upgrade to a fixed version: tox-dev filelock 4.2.1. Check the vendor advisory for mitigations.

References

• https://github.com/tox-dev/filelock/commit/740ff666b62a88496c8d7394e4e6230605e4d62b
• https://github.com/tox-dev/filelock/pull/843
• https://github.com/tox-dev/filelock/releases/tag/4.2.1
• https://github.com/tox-dev/filelock/security/advisories/GHSA-crv4-6mhj-j5jh

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