CVE-2025-68146

MEDIUM EPSS 8.1%
Published Dec 16, 20256mo ago · Modified Jun 17, 20261w ago
6.5 CVSS 3.1
Medium
Find Similar
Published Dec 16, 2025 6mo ago
Last Modified Jun 17, 2026 1w ago

Description

filelock is a platform-independent file lock for Python. In versions prior to 3.20.1, a Time-of-Check-Time-of-Use (TOCTOU) race condition allows local attackers to corrupt or truncate arbitrary user files through symlink attacks. The vulnerability exists in both Unix and Windows lock file creation where filelock checks if a file exists before opening it with O_TRUNC. An attacker can create a symlink pointing to a victim file in the time gap between the check and open, causing os.open() to follow the symlink and truncate the target file. All users of filelock on Unix, Linux, macOS, and Windows systems are impacted. The vulnerability cascades to dependent libraries. The attack requires local filesystem access and ability to create symlinks (standard user permissions on Unix; Developer Mode on Windows 10+). Exploitation succeeds within 1-3 attempts when lock file paths are predictable. The issue is fixed in version 3.20.1. If immediate upgrade is not possible, use SoftFileLock instead of UnixFileLock/WindowsFileLock (note: different locking semantics, may not be suitable for all use cases); ensure lock file directories have restrictive permissions (chmod 0700) to prevent untrusted users from creating symlinks; and/or monitor lock file directories for suspicious symlinks before running trusted applications. These workarounds provide only partial mitigation. The race condition remains exploitable. Upgrading to version 3.20.1 is strongly recommended.

CVSS Details

Base Score
6.5
Exploitability
1.0
Impact
5.5
Vector string
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:H/A:H
Attack Vector Local
Attack Complexity High
Privileges Required Low
User Interaction None
Scope Unchanged
Confidentiality Low
Integrity High
Availability High

Threat Intelligence

EPSS Exploit Probability
8.1% percentile
Exploit & Patch Status
Public Exploit Known
Patch Available

Weaknesses 3

CWE-362
CWE-367
CWE-59

Affected Products 1

VendorProductVersionRange
tox-devfilelock* <3.20.1

References 4

  • github.com https://github.com/tox-dev/filelock/commit/4724d7f8c3393ec1f048c93933e6e3e6ec321f0e
    Patch
  • github.com https://github.com/tox-dev/filelock/pull/461
    Issue TrackingPatch
  • github.com https://github.com/tox-dev/filelock/releases/tag/3.20.1
    ProductRelease Notes
  • github.com https://github.com/tox-dev/filelock/security/advisories/GHSA-w853-jp5j-5j7f
    ExploitMitigationVendor Advisory

Remediation

  • github.com https://github.com/tox-dev/filelock/commit/4724d7f8c3393ec1f048c93933e6e3e6ec321f0e
    Patch
  • github.com https://github.com/tox-dev/filelock/pull/461
    Issue TrackingPatch