MediumFix available
python-filelock — security advisory
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.
- Products
- python-filelock
- Affected versions
- 2.0.11-1, 2.0.12-1, 2.0.13-1, 3.0.0-2, 3.0.12-2, 3.0.3-1, 3.0.4-1, 3.12.2-1, 3.12.4-1, 3.13.1-1, 3.18.0-1, 3.20.0-1, 3.20.2-1, 3.20.3-1, 3.29.4-1, 3.3.2-1, 3.32.0-1, 3.32.2-1, 3.4.0-1, 3.4.2-1, 3.4.2-2, 3.6.0-1
- Fixed versions
- 3.0.4-1ubuntu0.1~esm1, 3.13.1-1ubuntu0.1~esm1, 3.6.0-1ubuntu0.1~esm1
- CVEs
- CVE-2026-22701
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 31 Oct 2026, 02:57 UTC · Revision 1
Source evidence
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.
osv:UBUNTU-CVE-2026-22701
python-filelock
Fixed versions: 3.0.4-1ubuntu0.1~esm1
python-filelock
Fixed versions: 3.6.0-1ubuntu0.1~esm1
python-filelock
Fixed versions: 3.13.1-1ubuntu0.1~esm1
python-filelock
Fixed versions: Not specified
python-filelock
Fixed versions: Not specified
python-filelock
Fixed versions: Not specified
Complete source record
{
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"url": "https://osv.dev/vulnerability/UBUNTU-CVE-2026-22701",
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