Time-of-check Time-of-use (TOCTOU) Race Condition 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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- published20 Oct 2026
- disclosed20 Oct 2026
- creditAnthropic's OSS Scanner
Introduced: 20 Oct 2026
NewCVE-2026-112941 (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 Time-of-check Time-of-use (TOCTOU) Race Condition via the strict lock implementation in _strict.py and related soft read-write storage code, where claim directories are created without being restricted to the owning account. A local attacker who can write to the same filesystem path can interfere with or substitute the claim directory, allowing unauthorized modification of lock state.