CVE-2026-112912: filelock: Symlink swap during SoftFileLock's writability check leaks whether a path exists and is writable by the lock taker

CVE-2026-112912 · Severity: low · CVSS 3.1 · Published 2026-10-20

filelock is a platform-independent file lock for Python. From 3.32.6 until 4.2.1, SoftFileLock can follow a swapped symbolic link during the conditional os.access writability check for a node without its owner-write bit, allowing another local user on a platform and directory configuration that follows the link to infer whether a chosen path exists and is writable from the observable acquisition result. This issue is fixed in version 4.2.1.

Technologies: filelock (PyPI). Vendors: PyPI.

Quick answers

Is CVE-2026-112912 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-112912 being exploited in the wild.
How severe is CVE-2026-112912?
Low severity, with a CVSS score of 3.1, published 20 October 2026.
Which products and versions are affected?
filelock (PyPI) >= 3.32.6, <= 4.2.0, ECOSYSTEM:introduced=3.32.6,fixed=4.2.1.
Is there a fix for CVE-2026-112912?
Yes. filelock (PyPI): upgrade to 4.2.1 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
Am I affected by CVE-2026-112912?
Check whether you run filelock (PyPI) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • filelock (PyPI): upgrade to 4.2.1 or later
    pip install "filelock>=4.2.1"

Affected products

  • filelock (PyPI) >= 3.32.6, <= 4.2.0, ECOSYSTEM:introduced=3.32.6,fixed=4.2.1

Identifiers

  • CVE-2026-112912
  • GHSA-9j6q-wvj5-jgjg

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