CVE-2026-22701 filelock Time-of-Check-Time-of-Use (TOCTOU) Symlink Vulnerability in SoftFileLock
Local attackers can exploit a race condition in SoftFileLock to cause denial of service or unexpected behavior via symlink manipulation.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-22701?
CVE-2026-22701 is a medium-severity vulnerability in tox-dev filelock, published on 10 Jan 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official 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.
Which versions are affected by CVE-2026-22701?
3 open source packages ship an affected version, including filelock. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
filelock PyPI | All versions | 3.20.3 |
filelock PyPI | All versions | 3.20.3 |
filelock PyPI | All versions | 3.20.3 |
Linux distribution packages (3)
python-filelock SUSE:Linux Enterprise Module for Development Tools 15 SP7 | All versions | 3.0.12-150100.3.9.1 |
python-filelock SUSE:Linux Enterprise Module for Package Hub 15 SP7 | All versions | 3.0.12-150100.3.9.1 |
python-filelock openSUSE:Tumbleweed | All versions | 3.20.3-1.1 |
Products include Tox-Dev Filelock.
How do I fix CVE-2026-22701?
Upgrade filelock to 3.20.3 or later.
Is CVE-2026-22701 being exploited?
There is no known exploitation of CVE-2026-22701 in the wild and no public exploit code.
Other vulnerabilities in tox-dev filelock
- CVE-2026-112940 filelock ReadWriteLock: SQLite reopens the lock database by name, so a planted symlink or journal file makes the lock user's process overwrite or unlink its own files
- CVE-2026-112911 filelock: StrictSoftFileLock and SoftReadWriteLock adopt a protocol directory another user created first, losing mutual exclusion
- CVE-2025-68146 filelock has TOCTOU race condition that allows symlink attacks during lock file creation
- CVE-2026-112909 filelock: UnixFileLock truncates and chmods any regular file another user renames or hard-links onto the lock path
- CVE-2026-112934 filelock: SoftReadWriteLock holder refresh writes through a hard link and hangs on a named pipe that another local user renames over its record
Sources
Also known as AZL-74234, AZL-79235, CLEANSTART-2026-BI98027, DEBIAN-CVE-2026-22701, ECHO-f048-f8f8-c11c, GHSA-qmgc-5h2g-mvrw and 15 more.