Medium severity · published Oct 20, 2026
CVE-2026-112909
filelock: UnixFileLock truncates and chmods any regular file another user renames or hard-links onto the lock path
6.1
CVSS
0.2%
EPSS
No
On KEV
Description
filelock is a platform-independent file lock for Python. Prior to 4.2.1, UnixFileLock can truncate a regular file renamed onto the lock path when another local user has actual rename permission, or hard-linked there under a permissive hard-link policy; when an explicit mode is requested, affected versions from 3.10.2 can also change that file's mode. This issue is fixed in version 4.2.1.
CVSS vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:H/A:N
Attack vector
Local
Complexity
Low
Privileges
Low
User interaction
None
Confidentiality
Low
Integrity
High
Availability
None
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.2% · higher than 11% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
FI
filelock · tox-dev
< 4.2.1 · source: vendor, NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-112909
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-112909
github.com
https://github.com/tox-dev/filelock/commit/e1e825b1992f69fb6b346dc395d5ae4893536c0a
github.com
https://github.com/tox-dev/filelock/pull/835
github.com
https://github.com/tox-dev/filelock/releases/tag/4.2.1
github.com
https://github.com/tox-dev/filelock/security/advisories/GHSA-69hj-f68j-2879
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7.1
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6.5
CVE-2025-68146
filelock has TOCTOU race condition that allows symlink attacks during lock file creation
6.3
CVE-2026-112911
filelock: StrictSoftFileLock and SoftReadWriteLock adopt a protocol directory another user created first, losing mutual exclusion
6.1
CVE-2026-112937
filelock: ReadWriteLock on the hard-link route deletes any directory another user renames onto its .filelock-* link directory name
6.1
CVE-2026-112936
filelock: ReadWriteLock follows a symlink at the lock path into SQLite