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OpenAdvisories
Medium · 5.3 CVE-2026-112910 EUVD-2026-117809GHSA-8mx5-7m5m-r77g

filelock: WindowsFileLock ignores mode: a 0o600 lock file and the ReadWriteLock database inherit the directory ACL

Published Nov 5, 2026 · Updated Nov 9, 2026 · Assigned by GitHub_M

Description

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.

Affected products

VendorProductAffectedFixed
tox-dev filelock >= 3.10.0, < 4.2.1 —

Fixed in Linux distributions

Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.

ReleasePackageFixed inAdvisory
Ubuntu 26.10 python-filelock No fix yet —
Ubuntu 26.04 LTS python-filelock No fix yet —
Show 4 more (older releases, extended support, other products)
ReleasePackageFixed inAdvisory
Ubuntu Pro 24.04 LTS python-filelock No fix yet —
Ubuntu Pro 22.04 LTS python-filelock No fix yet —
Ubuntu Pro 20.04 LTS python-filelock No fix yet —
Ubuntu Pro 18.04 LTS python-filelock No fix yet —

Azure Linux

ReleasePackageFixed inAdvisory
Azure Linux 3 python-filelock No fix yet —

Wolfi

ReleasePackageFixed inAdvisory
Wolfi rolling superset-6.1 6.1.0-r23 —

Affected packages

EcosystemPackageAffectedFixedRecord
PyPI filelock >= 3.10.0, < 4.2.1 4.2.1 GHSA-8mx5-7m5m-r77g

References