Medium severity · published Oct 20, 2026
CVE-2026-112911
filelock: StrictSoftFileLock and SoftReadWriteLock adopt a protocol directory another user created first, losing mutual exclusion
6.3
CVSS
0.1%
EPSS
No
On KEV
Description
filelock is a platform-independent file lock for Python. From 3.30.0 until 4.2.1, StrictSoftFileLock versions from 3.30.0 and SoftReadWriteLock versions from 4.0.0 can adopt a protocol directory created first by another local user in a shared parent directory, allowing that user to alter protocol state and admit concurrent holders. This issue is fixed in version 4.2.1.
CVSS vector
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:H
Attack vector
Local
Complexity
High
Privileges
Low
User interaction
None
Confidentiality
None
Integrity
High
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.1% · higher than 4% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
FI
filelock · tox-dev
>= 3.30.0, < 4.2.1 · source: vendor, NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-112911
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-112911
Patch
https://github.com/tox-dev/filelock/commit/bfa066d65a1ba9106f86ee9d027f7588b9c77e03
Patch
https://github.com/tox-dev/filelock/pull/839
Release Notes
https://github.com/tox-dev/filelock/releases/tag/4.2.1
Exploit
https://github.com/tox-dev/filelock/security/advisories/GHSA-9c4x-gm8v-wgc4
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