Time-of-check Time-of-use (TOCTOU) Race Condition Affecting filelock package, versions [,3.20.1)
Threat Intelligence
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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- published17 Dec 2025
- disclosed16 Dec 2025
- creditGeorge Tsigourakos
Introduced: 16 Dec 2025
CVE-2025-68146 (opens in a new tab)How to fix?
Upgrade filelock to version 3.20.1 or higher.
Overview
Affected versions of this package are vulnerable to Time-of-check Time-of-use (TOCTOU) Race Condition during lock file creation. An attacker can corrupt or truncate arbitrary files by exploiting a race condition between the existence check and file opening with O_TRUNC, allowing the creation of a symlink that is followed and results in the target file being truncated.
Note:
This is only exploitable if the attacker has local filesystem access and the ability to create symlinks in the lock file directory.
Workaround
This vulnerability can be mitigated by using SoftFileLock instead of UnixFileLock/WindowsFileLock, ensuring lock file directories have restrictive permissions (chmod 0700), and monitoring lock file directories for suspicious symlinks before running trusted applications.