Symlink Attack Affecting filelock package, versions [3.20.4,4.0.9)
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-21280754
- published20 Oct 2026
- disclosed20 Oct 2026
- creditKevin Stubbings
Introduced: 20 Oct 2026
NewCVE-2026-112936 (opens in a new tab)How to fix?
Upgrade filelock to version 4.0.9 or higher.
Overview
Affected versions of this package are vulnerable to Symlink Attack via ReadWriteLock in src/filelock/_read_write.py, which resolves the lock file path using Path.resolve() before passing it to sqlite3.connect(). An attacker who can plant a symlink in a shared lock directory can cause the victim process to open, lock, or create the symlink's target instead of the intended lock file. By repointing the symlink between two lock constructions, two writers can simultaneously hold the lock, breaking mutual exclusion and allowing unauthorized file writes.