---
id: CVE-2026-112906
title: >-
  filelock: SoftFileLock evicts a fresh lock file whose watched age another
  local user's pre-dated file passed on through inode reuse
summary: >-
  filelock is a platform-independent file lock for Python. From 4.1.0 until
  4.2.1, SoftFileLock versions from 4.1.0 can reuse a stale observation when an
  attacker pre-dates and removes its own marker, at least two lock-user
  processes are w…
severity: medium
cvss: 4.7
cvssVector: 'CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:N'
cvssSource: cna
cwe:
  - CWE-694
vendor: tox-dev
product: filelock
affected:
  - 'filelock >= 4.1.0, < 4.2.1'
ssvc:
  exploitation: poc
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-10-20T15:27:04.618631Z'
exploitAvailable: true
published: '2026-10-20'
updated: '2026-10-20'
sourceUpdated: '2026-10-20T15:27:25.903Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-112906'
references:
  - url: >-
      https://github.com/tox-dev/filelock/security/advisories/GHSA-2g95-wg33-c5x2
    label: >-
      https://github.com/tox-dev/filelock/security/advisories/GHSA-2g95-wg33-c5x2
  - url: >-
      https://github.com/tox-dev/filelock/commit/740ff666b62a88496c8d7394e4e6230605e4d62b
    label: >-
      https://github.com/tox-dev/filelock/commit/740ff666b62a88496c8d7394e4e6230605e4d62b
  - 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
  - exploit-available
ingestedAt: '2026-10-20T15:09:24.131Z'
---

## Overview

filelock is a platform-independent file lock for Python. From 4.1.0 until 4.2.1, SoftFileLock versions from 4.1.0 can reuse a stale observation when an attacker pre-dates and removes its own marker, at least two lock-user processes are waiting, coarse or matching modification times preserve the observation, and an honest contender creates a fresh marker on the reused inode, causing that live marker to be removed as stale. This issue is fixed in version 4.2.1.

## Affected

- `filelock >= 4.1.0, < 4.2.1`

## Remediation

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