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.
Metrics
Affected Vendors & Products
References
History
Sat, 10 Jan 2026 06:15:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | 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. | |
| Title | filelock Time-of-Check-Time-of-Use (TOCTOU) Symlink Vulnerability in SoftFileLock | |
| Weaknesses | CWE-362 CWE-367 CWE-59 |
|
| References |
| |
| Metrics |
cvssV3_1
|
Status: PUBLISHED
Assigner: GitHub_M
Published: 2026-01-10T05:59:28.872Z
Updated: 2026-01-10T05:59:28.872Z
Reserved: 2026-01-08T19:23:09.856Z
Link: CVE-2026-22701
No data.
Status : Received
Published: 2026-01-10T06:15:52.673
Modified: 2026-01-10T06:15:52.673
Link: CVE-2026-22701
No data.