CVE-2026-22701
MEDIUM
GHSA-qmgc-5h2g-mvrw
CVSS Vector
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:H
Lifecycle Timeline
3Description
filelock is a platform-independent file lock for Python. Prior to version 3.20.3, a TOCTOU race condition vulnerability exists in the SoftFileLock implementation of the filelock package. An attacker with local filesystem access and permission to create symlinks can exploit a race condition between the permission validation and file creation to cause lock operations to fail or behave unexpectedly. The vulnerability occurs in the _acquire() method between raise_on_not_writable_file() (permission check) and os.open() (file creation). During this race window, an attacker can create a symlink at the lock file path, potentially causing the lock to operate on an unintended target file or leading to denial of service. This issue has been patched in version 3.20.3.
Analysis
Python's filelock SoftFileLock implementation prior to version 3.20.3 contains a TOCTOU race condition that allows local attackers with symlink creation privileges to interfere with lock file operations between permission validation and file creation. An attacker can exploit this window to create a symlink at the target lock path, causing lock operations to fail or redirect to unintended files, resulting in denial of service or unexpected behavior. …
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Remediation
Within 30 days: Identify affected systems and apply vendor patches as part of regular patch cycle. Vendor patch is available.
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