CVE-2026-112935 filelock: SoftFileLock stale-lock break removes a live lock file on a reused inode number and admits two holders
- Exploited in the wild
- Not known
- Fix
- Available
What is CVE-2026-112935?
CVE-2026-112935 is a medium-severity vulnerability in tox-dev filelock, published on 20 Oct 2026.
Official description
filelock is a platform-independent file lock for Python. From 3.22.0 until 4.2.1, SoftFileLock can break a stale marker after an attacker frees its own marker following the stale read, an honest contender creates a live successor on the reused inode, and the successor's modification time is not newer than the saved observation, causing the live marker to be removed and two holders to be admitted. This issue is fixed in version 4.2.1.
Weakness: CWE-367
Which versions are affected by CVE-2026-112935?
2 open source packages ship an affected version, including filelock. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
filelock PyPI | From 3.22.0 | 4.2.1 |
filelock PyPI | From 3.22.0 | 4.2.1 |
Products include Tox-Dev Filelock.
How do I fix CVE-2026-112935?
Upgrade filelock to 4.2.1 or later.
Is CVE-2026-112935 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-112935 exists.
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-110070, CLEANSTART-2026-NT53599, DEBIAN-CVE-2026-112935, GHSA-fq56-3cx3-fjxp, MINI-pqrp-pc6v-6g6c, UBUNTU-CVE-2026-112935.