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Vulnerabilities

Security fix · CVE-2026-112909

filelock is a platform-independent file lock for Python.

Published Oct 20, 2026 · catalog updated Oct 28, 2026 · filelock is a platform-independent

Last checked Nov 3, 2026. A connected source was read within the last 7 days.

Check if you run it

No confirmed exploitation is on record for CVE-2026-112909. EPSS is 0.22%. Act only if a listed version of filelock is a platform-independent is installed.

Gaps on this record

  • The stored product name is a package slug. The name on this page is taken from the title (filelock is a platform-independent).
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
Medium6.1
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.22%
Remediation
Version ranges on file
Affected products
pip filelock · pypi filelock

, the backend of and on Unix, empties whatever regular file it finds at the lock path once it holds the (a kernel lock on an open file). With an explicit it also chmods that file (sets its permission bits), whether or not this acquire created it. Another local user who can rename or hard-link one of the files of the user running the lock (below: the lock user) onto the lock path gets that file truncated by the lock user's next . A hard link is a second name for the same file. With a mode such as the file, still owned by the lock user, also becomes readable and writable by that other user. The other user can then read and alter everything the lock user writes to it afterwards. , the defence added for the symlink variant (CVE-2025-68146), does not see a renamed file or a hard link. The rename route needs the file's directory to be writable without the sticky bit (a directory flag that lets only a file's owner remove or rename it). The hard-link route into a sticky directory such as needs , a Linux kernel setting. Affected versions are every filelock release up to and including 4.2.0 (the truncation is as old as the project; the chmod since 3.10.2). Anthropic's OSS Scanner reported this in private. Finding covered by this advisory: - [high, CWE-706]: UnixFileLock truncates and chmods victim files renamed onto the lock path. ## Severity **CVSS 3.1 scores 6.1 (Medium).** (local): the other user needs an account on the same host. (low privileges): an ordinary account is enough. (no user interaction). (low attack complexity): one rename or link, then wait for the lock user's next acquire; no race. (high integrity impact): the lock user's own process truncates a file it did not mean to touch, including content behind a second name the other user could neither modify nor delete. With a permissive explicit the other user can then write to it. If that file is one the lock user later executes or trusts, that is code execution as the lock user. (partial confidentiality impact):

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • pip filelock<= 4.2.0
  • pypi filelockversion unspecified

How to fix CVE-2026-112909

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-112909. EPSS is 0.22%. Act only if a listed version of filelock is a platform-independent is installed.

Which versions are affected?

Compare what you have installed with <= 4.2.0. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-706. EPSS 0.22%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. Oct 20, 2026 · NIST NVD

    Detected

    filelock is a platform-independent file lock for Python. Prior to 4.2.1, UnixFileLock can truncate a regular file renamed onto the lock path when another local user has actual rename permission, or hard-linked there under a permissive hard-link policy; when an explicit mode is requested, affected versions from 3.10.2 can also change that file's mode. This issue is fixed in version 4.2.1.

  2. Oct 20, 2026 · NIST NVD

    Updated

    filelock is a platform-independent file lock for Python. Prior to 4.2.1, UnixFileLock can truncate a regular file renamed onto the lock path when another local user has actual rename permission, or hard-linked there under a permissive hard-link policy; when an explicit mode is requested, affected versions from 3.10.2 can also change that file's mode. This issue is fixed in version 4.2.1.

  3. Oct 28, 2026 · GitHub Advisory Database

    Updated

    , the backend of and on Unix, empties whatever regular file it finds at the lock path once it holds the (a kernel lock on an open file). With an explicit it also chmods that file (sets its permission bits), whether or not this acquire created it. Another local user who can rename or hard-link one of the files of the user running the lock (below: the lock user) onto the lock path gets that file tru

Sources

  • CVE.orgVulnerability recordCVE-2026-112909

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2026-112909

    30-day exploitation probability 0.22%

    first.org
  • GitHub Advisory DatabasePackage advisoryGHSA-69hj-f68j-2879

    filelock: UnixFileLock truncates and chmods any regular file another user renames or hard-links onto the lock path

    github.com
  • GitLab Advisory DatabasePackage advisoryCVE-2026-112909

    UnixFileLock, the backend of FileLock and AsyncFileLock on Unix, empties whatever regular file it finds at the lock path once it holds the flock (a kernel lock on an open file). With an explicit mode it also chmods that file (sets its permission bits), whether or not this acquire created it. Another local user who can rename or hard-link one of the files of the user running the lock (below: …

    advisories.gitlab.com
  • NIST NVDVulnerability recordCVE-2026-112909

    filelock is a platform-independent file lock for Python. Prior to 4.2.1, UnixFileLock can truncate a regular file renamed onto the lock path when another local user has actual rename permission, or hard-linked there under a permissive hard-link policy; when an explicit mode is re

    nvd.nist.gov

References

Freshness

Last verified in this catalog Nov 3, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.

  • FIRST EPSSNov 3, 2026
  • GitLab Advisory DatabaseOct 30, 2026
  • GitHub Advisory DatabaseOct 29, 2026
  • CVE.orgOct 21, 2026
  • NIST NVDOct 21, 2026