CVE-2025-68146: medium-severity vulnerability in tox-dev filelock
filelock has TOCTOU race condition that allows symlink attacks during lock file creation
Published · Updated
E-mail alert when it lands in KEV, gets a public PoC or its score goes up.
13Vexday Risk Score
No sign of exploitation. No public exploitation artifact known so far.
ssvc Trackcvss 6.3epss 0.2%
filelock is a platform-independent file lock for Python. In versions prior to 3.20.1, a Time-of-Check-Time-of-Use (TOCTOU) race condition allows local attackers to corrupt or truncate arbitrary user files through symlink attacks. The vulnerability exists in both Unix and Windows lock file creation where filelock checks if a file exists before opening it with O_TRUNC. An attacker can create a symlink pointing to a victim file in the time gap between the check and open, causing os.open() to follow the symlink and truncate the target file. All users of filelock on Unix, Linux, macOS, and Windows systems are impacted. The vulnerability cascades to dependent libraries. The attack requires local filesystem access and ability to create symlinks (standard user permissions on Unix; Developer Mode on Windows 10+). Exploitation succeeds within 1-3 attempts when lock file paths are predictable. The issue is fixed in version 3.20.1. If immediate upgrade is not possible, use SoftFileLock instead of UnixFileLock/WindowsFileLock (note: different locking semantics, may not be suitable for all use cases); ensure lock file directories have restrictive permissions (chmod 0700) to prevent untrusted users from creating symlinks; and/or monitor lock file directories for suspicious symlinks before running trusted applications. These workarounds provide only partial mitigation. The race condition remains exploitable. Upgrading to version 3.20.1 is strongly recommended.
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:H
Affected products
tox-dev · filelockRelated CVEs — tox-dev filelock
In the same product, most dangerous first.
CVE-2026-112934MEDIUMfilelock: SoftReadWriteLock holder refresh writes through a hard link and hangs on a named pipe that another local user renames over its recordEPSS 0.2%CVE-2026-112936MEDIUMfilelock: ReadWriteLock follows a symlink at the lock path into SQLiteEPSS 0.2%CVE-2026-112909MEDIUMfilelock: UnixFileLock truncates and chmods any regular file another user renames or hard-links onto the lock pathEPSS 0.2%CVE-2026-112915MEDIUMfilelock ReadWriteLock: a crafted lock database makes every acquire stall or hang regardless of timeoutEPSS 0.2%CVE-2026-112912LOWfilelock: Symlink swap during SoftFileLock's writability check leaks whether a path exists and is writable by the lock takerEPSS 0.2%CVE-2026-112940HIGHfilelock 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 filesEPSS 0.2%