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OpenAdvisories
Medium · 6.3 CVE-2026-112911 EUVD-2026-105018GHSA-9c4x-gm8v-wgc4

filelock: StrictSoftFileLock and SoftReadWriteLock adopt a protocol directory another user created first, losing mutual exclusion

Published Oct 20, 2026 · Updated Oct 28, 2026 · Assigned by GitHub_M

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.

Affected products

VendorProductAffectedFixed
tox-dev filelock >= 3.30.0, < 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
Debian 14 python-filelock 4.2.8-1 —
Debian 13 python-filelock No fix yet —
Debian 12 python-filelock No fix yet —
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 —

Wolfi

ReleasePackageFixed inAdvisory
Wolfi rolling py3.10-filelock No fix yet —

Affected packages

EcosystemPackageAffectedFixedRecord
PyPI filelock >= 3.30.0, < 4.2.1 4.2.1 GHSA-9c4x-gm8v-wgc4

References