Race Condition Enabling Link Following Affecting filelock package, versions [4.1.0,4.2.1)
Threat Intelligence
Snyk has a proof-of-concept or detailed explanation of how to exploit this vulnerability.
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Test your applications- Snyk IDSNYK-PYTHON-FILELOCK-21280757
- published20 Oct 2026
- disclosed20 Oct 2026
- creditAnthropic's OSS Scanner
Introduced: 20 Oct 2026
NewCVE-2026-112914 (opens in a new tab)How to fix?
Upgrade filelock to version 4.2.1 or higher.
Overview
Affected versions of this package are vulnerable to Race Condition Enabling Link Following via SoftFileLock._try_break_stale_lock in src/filelock/_soft.py, which can restore a stale marker by name after moving it aside. A local attacker with rename access in a non-sticky lock directory can swap in a symbolic link, causing the lock user to hard-link one of its own files into the lock directory on a runtime that follows the link and a same-filesystem target. This allows the attacker to break a live lock and achieve unauthorized write access to files owned by the victim process.
Note: This is only exploitable when another local user has rename access in a non-sticky lock directory, and no other user can replace the lock directory or any of its ancestors.