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GHSA-9c4x-gm8v-wgc4: filelock: StrictSoftFileLock and SoftReadWriteLock adopt a protocol directory another user created first, losing mutual exclusion
- Identifiers
- CVE-2026-112911GHSA-9c4x-gm8v-wgc4
- Published
- Record updated
- Affected
- filelock >= 3.30.0, <= 4.2.0
- Fixed in
- 4.2.1
- Known exploitation
- Not listed in the CISA Known Exploited Vulnerabilities catalog at the last check.
- EPSS
- 0.1%
Summary
The `StrictSoftFileLock`, `AsyncStrictSoftFileLock`, `SoftReadWriteLock` and `AsyncSoftReadWriteLock` classes in filelock 3.30.0 through 4.2.0 adopt an existing protocol directory (`<path>.filelock/claims` or `<path>.rw/{gen,holders}`) after checking only that it is a real directory, not who owns it. A local user who creates that directory first in a shared directory such as `/tmp` can delete the lock user's claims, letting a second process enter the critical section without error, and against `SoftReadWriteLock` can redirect file writes or stall acquires. The finding is tracked as CVE-less GHSA-9c4x-gm8v-wgc4 (ANT-2026-Q5VK5JEE), rated CVSS 6.3 (Medium).
Mitigation
The source does not state a fix yet. Check the original advisory for updates.
Affected packages in the Exposure Registry
Matched by package name and ecosystem. Each entry shows whether the package delegates to a language model and how many tracked packages depend on it.
- filelockPyPINo LLM dependency detected · 42 tracked dependents