---
id: CVE-2026-112940
title: >-
  filelock ReadWriteLock: SQLite reopens the lock database by name, so a planted
  symlink or journal file makes the lock user's process overwrite or unlink its
  own files
summary: >-
  filelock is a platform-independent file lock for Python. From 3.20.4 until
  4.2.1, ReadWriteLock let SQLite reopen the database and side files by name; on
  POSIX systems an attacker with rename access in a non-sticky parent can swap
  those …
severity: high
cvss: 7.1
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H'
cvssSource: cna
cwe:
  - CWE-363
vendor: tox-dev
product: filelock
affected:
  - 'filelock >= 3.20.4, < 4.2.1'
published: '2026-10-20'
updated: '2026-10-20'
sourceUpdated: '2026-10-20T14:41:49.555Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-112940'
references:
  - url: >-
      https://github.com/tox-dev/filelock/security/advisories/GHSA-v4x8-3wr5-3wq8
    label: >-
      https://github.com/tox-dev/filelock/security/advisories/GHSA-v4x8-3wr5-3wq8
  - url: 'https://github.com/tox-dev/filelock/pull/834'
    label: 'https://github.com/tox-dev/filelock/pull/834'
  - url: >-
      https://github.com/tox-dev/filelock/commit/5e3f2ec0c5fb17cb2635b60b2b68bc63ab81ca2d
    label: >-
      https://github.com/tox-dev/filelock/commit/5e3f2ec0c5fb17cb2635b60b2b68bc63ab81ca2d
  - url: 'https://github.com/tox-dev/filelock/releases/tag/4.2.1'
    label: 'https://github.com/tox-dev/filelock/releases/tag/4.2.1'
tags:
  - cve.org
ingestedAt: '2026-10-20T15:09:24.118Z'
---

## Overview

filelock is a platform-independent file lock for Python. From 3.20.4 until 4.2.1, ReadWriteLock let SQLite reopen the database and side files by name; on POSIX systems an attacker with rename access in a non-sticky parent can swap those names to cause overwrite or unlink operations, while a writable adjacent hot journal is additionally required for attacker-chosen content overwrites. This issue is fixed in version 4.2.1.

## Affected

- `filelock >= 3.20.4, < 4.2.1`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.