# CVE-2026-112910: filelock: WindowsFileLock ignores mode: a 0o600 lock file and the ReadWriteLock database inherit the directory ACL

Status: published. Published: 2026-11-05. Updated: 2026-11-05.

filelock is a platform-independent file lock for Python. From 3.10.0 until 4.2.1, filelock on Windows ignores the mode argument for WindowsFileLock files and the ReadWriteLock SQLite database. A lock created with mode=0o600 receives the parent directory's inheritable ACL because _open_non_reparse_fd and _nt_open do not create an owner-only security descriptor. Another local account with inherited access can read holder metadata or the lock database, modify those files where the ACL permits writes, or take the byte-range lock after release and delay later acquisitions. UnixFileLock is not affected, and mutual exclusion between cooperating processes continues to hold. This issue is fixed in version 4.2.1.

## Remediation

- fix: filelock (PyPI): OSV reports a fixed version 4.2.1. Check the advisory for supported release branches. (source: OSV GHSA-8mx5-7m5m-r77g) — https://github.com/advisories/GHSA-8mx5-7m5m-r77g

## Affected products and versions

- tox-dev / filelock: >= 3.10.0, < 4.2.1 (affected). Source: CNA: GitHub_M
-  / filelock (filelock): 3.10.0 (affected, PyPI); 3.10.1 (affected, PyPI); 3.10.2 (affected, PyPI); 3.10.3 (affected, PyPI); 3.10.4 (affected, PyPI); 3.10.5 (affected, PyPI); 3.10.6 (affected, PyPI); 3.10.7 (affected, PyPI); 3.11.0 (affected, PyPI); 3.12.0 (affected, PyPI); 3.12.1 (affected, PyPI); 3.12.2 (affected, PyPI); 3.12.3 (affected, PyPI); 3.12.4 (affected, PyPI); 3.13.0 (affected, PyPI); 3.13.1 (affected, PyPI); 3.13.2 (affected, PyPI); 3.13.3 (affected, PyPI); 3.13.4 (affected, PyPI); 3.14.0 (affected, PyPI); 3.15.0 (affected, PyPI); 3.15.1 (affected, PyPI); 3.15.2 (affected, PyPI); 3.15.3 (affected, PyPI); 3.15.4 (affected, PyPI); 3.16.0 (affected, PyPI); 3.16.1 (affected, PyPI); 3.17.0 (affected, PyPI); 3.18.0 (affected, PyPI); 3.19.1 (affected, PyPI); 3.20.0 (affected, PyPI); 3.20.1 (affected, PyPI); 3.20.2 (affected, PyPI); 3.20.3 (affected, PyPI); 3.20.4 (affected, PyPI); 3.21.0 (affected, PyPI); 3.21.1 (affected, PyPI); 3.21.2 (affected, PyPI); 3.22.0 (affected, PyPI); 3.23.0 (affected, PyPI); 3.24.0 (affected, PyPI); 3.24.1 (affected, PyPI); 3.24.2 (affected, PyPI); 3.24.3 (affected, PyPI); 3.25.0 (affected, PyPI); 3.25.1 (affected, PyPI); 3.25.2 (affected, PyPI); 3.28.0 (affected, PyPI); 3.29.0 (affected, PyPI); 3.29.1 (affected, PyPI); 3.29.2 (affected, PyPI); 3.29.3 (affected, PyPI); 3.29.4 (affected, PyPI); 3.29.5 (affected, PyPI); 3.29.6 (affected, PyPI); 3.29.7 (affected, PyPI); 3.30.0 (affected, PyPI); 3.30.1 (affected, PyPI); 3.30.2 (affected, PyPI); 3.30.3 (affected, PyPI); 3.31.0 (affected, PyPI); 3.31.1 (affected, PyPI); 3.31.2 (affected, PyPI); 3.32.0 (affected, PyPI); 3.32.2 (affected, PyPI); 3.32.3 (affected, PyPI); 3.32.4 (affected, PyPI); 3.32.5 (affected, PyPI); 3.32.6 (affected, PyPI); 3.32.7 (affected, PyPI); 4.0.0 (affected, PyPI); 4.0.1 (affected, PyPI); 4.0.10 (affected, PyPI); 4.0.11 (affected, PyPI); 4.0.12 (affected, PyPI); 4.0.2 (affected, PyPI); 4.0.3 (affected, PyPI); 4.0.4 (affected, PyPI); 4.0.5 (affected, PyPI); 4.0.6 (affected, PyPI); 4.0.7 (affected, PyPI); 4.0.8 (affected, PyPI); 4.0.9 (affected, PyPI); 4.1.0 (affected, PyPI); 4.1.1 (affected, PyPI); 4.1.2 (affected, PyPI); 4.2.0 (affected, PyPI); Ecosystem version events: introduced 3.10.0; fixed 4.2.1. Source: OSV GHSA-8mx5-7m5m-r77g

## Severity and prioritization

- CVSS 3.1: 5.3 (medium); CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L; source: CNA: GitHub_M

- CISA KEV: No listing in collected sources

- EPSS: Not available

- SSVC: Not available

- Weaknesses: CWE-732

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://github.com/tox-dev/filelock/security/advisories/GHSA-8mx5-7m5m-r77g (CNA: GitHub_M; x_refsource_CONFIRM)

- https://github.com/tox-dev/filelock/pull/835 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/tox-dev/filelock/commit/72786d41aa25159ad28c1bcf4291738b135b2c6c (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/tox-dev/filelock/commit/e1e825b1992f69fb6b346dc395d5ae4893536c0a (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/tox-dev/filelock/releases/tag/4.2.1 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/advisories/GHSA-8mx5-7m5m-r77g (OSV / GitHub Security Advisories; advisory)

- https://osv.dev/vulnerability/GHSA-8mx5-7m5m-r77g (OSV / GitHub Security Advisories; osv)

## Provenance

- CNA: GitHub_M: https://www.cve.org/CVERecord?id=CVE-2026-112910; retrieved 2026-11-05; source updated 2026-11-05

- OSV / GitHub Security Advisories: https://osv.dev/vulnerability/GHSA-8mx5-7m5m-r77g; retrieved 2026-11-05; source updated 2026-10-28

Revision: e3652ff8870c957f80c349b82577d4630fed0a7f67a99cf0cda5cdf1c9c75ef7

Canonical: https://y2.dev/cve/CVE-2026-112910

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