# CVE-2026-112937: filelock ReadWriteLock insecure temporary directory cleanup

Source: https://junglewise.ai/threats/cve-2026-112937-filelock-is-a-platform-independent-file-lock-for-python-from-4-1  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-20. Updated: 2026-10-20  
License: CC BY 4.0 with a link back

CVE-2026-112937 · Severity: medium · CVSS 6.1 · Published 2026-10-20

filelock is a Python library providing cross-platform file locking for applications. A flaw in the ReadWriteLock component allows local attackers to exploit insecure cleanup of temporary directories, potentially leading to unauthorized file operations or data tampering by other users on the same system.

Technologies: [filelock (PyPI)](https://junglewise.ai/threats/technologies/filelock), [Tox-Dev Filelock](https://junglewise.ai/threats/technologies/tox-dev-filelock). Vendors: [PyPI](https://junglewise.ai/threats/vendors/pypi), [Tox-Dev](https://junglewise.ai/threats/vendors/tox-dev).

## Quick answers

**Is CVE-2026-112937 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-112937 being exploited in the wild.

**How severe is CVE-2026-112937?** Medium severity, with a CVSS score of 6.1, published 20 October 2026.

**Which products and versions are affected?** filelock (PyPI) >= 4.1.0, <= 4.2.0, ECOSYSTEM:introduced=4.1.0,fixed=4.2.1; Tox-Dev Filelock 4.1.0 to 4.2.1.

**Is there a fix for CVE-2026-112937?** 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.

**How is CVE-2026-112937 attacked?** It is attacked with local access.

**Am I affected by CVE-2026-112937?** Check whether you run filelock (PyPI) or Tox-Dev Filelock 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

  ```sh
  pip install "filelock>=4.2.1"
  ```


## Technical details

The vulnerability exists in filelock versions 4.1.0 through 4.2.1 where ReadWriteLock can remove randomized .filelock-* private hard-link directories during cleanup. An attacker with local access and rename permissions in a non-sticky parent directory can observe live names or craft a dead-owner sweep name, then rename a sibling directory onto it for deletion. The attack requires local access and write permissions in the parent directory containing the lock files.

## Affected products

- tox-dev filelock 4.1.0 to 4.2.1

## Identifiers

- CVE-2026-112937
- GHSA-jqc4-5cvw-7w85

## Timeline

- 2026-10-20: disclosed

## References

- [https://github.com/tox-dev/filelock/commit/5e3f2ec0c5fb17cb2635b60b2b68bc63ab81ca2d](https://github.com/tox-dev/filelock/commit/5e3f2ec0c5fb17cb2635b60b2b68bc63ab81ca2d)
- [https://github.com/tox-dev/filelock/pull/834](https://github.com/tox-dev/filelock/pull/834)

## Related threats

- [filelock StrictSoftFileLock symlink race privilege escalation](https://junglewise.ai/threats/cve-2026-112938-filelock-strictsoftfilelock-follows-a-symbolic-link-swapped-in)
- [filelock: ReadWriteLock on Windows acts on SQLite side files another local user places beside its database](https://junglewise.ai/threats/cve-2026-112913-filelock-readwritelock-on-windows-acts-on-sqlite-side-files)
- [filelock WindowsFileLock mode parameter permission enforcement failure](https://junglewise.ai/threats/cve-2026-112910-filelock-windowsfilelock-ignores-mode-a-0o600-lock-file-and-the)
- [filelock StrictSoftFileLock directory permission bypass](https://junglewise.ai/threats/cve-2026-112908-filelock-strictsoftfilelock-creates-its-claim-directories)
- [filelock: On Windows an oplock on a soft lock's marker holds SoftFileLock.acquire() past its timeout and blocks the stale break](https://junglewise.ai/threats/cve-2026-112907-filelock-on-windows-an-oplock-on-a-soft-lock-s-marker-holds)