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Vulnerabilities

Security fix · CVE-2026-112914

filelock is a platform-independent file lock for Python.

Published Oct 20, 2026 · catalog updated Oct 23, 2026 · filelock is a platform-independent

Check if you run it

No confirmed exploitation is on record for CVE-2026-112914. EPSS is 0.10%. 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
Medium5.3
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.10%
Remediation
Version ranges on file
Affected products
cpe tox-dev/filelock · pip filelock · pypi filelock

When a soft-lock stale break finds that the marker (the lock file at ) it renamed aside was a live one recreated by a successor, the restore branch of checks the break name with (a check that reads a name without following a symbolic link) and then calls by name. On CPython 3.12 and later on Linux (and on macOS) that call follows a symbolic link (a file that redirects to another path). A local user (the other user below) who can write a shared lock directory without the sticky bit (a directory flag that lets only a file's owner rename or remove it) replaces the break name with a symbolic link between those two calls. The , , or break of the user running the lock (the lock user below) then creates a hard link (a second name for the same file), in that directory, to any of the lock user's own files on the same filesystem. That includes files inside directories the other user cannot enter and links that (a Linux setting that forbids hard links to files one does not own) refuses the other user when it asks itself. The link exposes the file's size, times, mode and owner, keeps the inode (the kernel's identity for a file, independent of its name) alive, and gives the other user a name it can move. On 4.2.0 a later of the lock user on that name truncated the file. Affected versions: filelock >= 4.1.0 and <= 4.2.0 (finding ). ## Severity **CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:H/A:N, 5.3 (Medium).** (local): the other user needs an account on the same host. (high attack complexity): two short races against a few lines of Python, timed by inotify (a Linux facility that reports file events), and the lock user must take the lock again and again (the scanner won 10 runs out of 10 after 9 to 910 lock cycles). (low privileges): an unprivileged account is enough. (no user interaction): the lock user's process acts on its own. (low confidentiality impact): the file's metadata through the new name, not its content. (high integrity impact): the other user chooses the file, and whate

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.

  • cpe tox-dev/filelock< 4.2.1
  • pip filelock>= 4.1.0, <= 4.2.0
  • pypi filelockversion unspecified

How to fix CVE-2026-112914

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-2026-112914. EPSS is 0.10%. Act only if a listed version of filelock is a platform-independent is installed.

Which versions are affected?

Compare what you have installed with < 4.2.1, >= 4.1.0, <= 4.2.0. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-363; CWE-59: Link Following. EPSS 0.10%. 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. From 4.1.0 until 4.2.1, SoftFileLock can restore a stale marker by name after moving it aside, allowing another local user with rename access in a non-sticky lock directory to swap in a symbolic link and, on a runtime that follows the link and a same-filesystem target, make the lock user hard-link one of its files into the lock directory. Th

  2. Oct 20, 2026 · NIST NVD

    Updated

    filelock is a platform-independent file lock for Python. From 4.1.0 until 4.2.1, SoftFileLock can restore a stale marker by name after moving it aside, allowing another local user with rename access in a non-sticky lock directory to swap in a symbolic link and, on a runtime that follows the link and a same-filesystem target, make the lock user hard-link one of its files into the lock directory. Th

  3. Oct 21, 2026 · NIST NVD

    Updated

    filelock is a platform-independent file lock for Python. From 4.1.0 until 4.2.1, SoftFileLock can restore a stale marker by name after moving it aside, allowing another local user with rename access in a non-sticky lock directory to swap in a symbolic link and, on a runtime that follows the link and a same-filesystem target, make the lock user hard-link one of its files into the lock directory. Th

  4. Oct 21, 2026 · NIST NVD

    Updated

    filelock is a platform-independent file lock for Python. From 4.1.0 until 4.2.1, SoftFileLock can restore a stale marker by name after moving it aside, allowing another local user with rename access in a non-sticky lock directory to swap in a symbolic link and, on a runtime that follows the link and a same-filesystem target, make the lock user hard-link one of its files into the lock directory. Th

  5. Oct 23, 2026 · GitHub Advisory Database

    Updated

    When a soft-lock stale break finds that the marker (the lock file at ) it renamed aside was a live one recreated by a successor, the restore branch of checks the break name with (a check that reads a name without following a symbolic link) and then calls by name. On CPython 3.12 and later on Linux (and on macOS) that call follows a symbolic link (a file that redirects to another path). A local use

Sources

  • CVE.orgVulnerability recordCVE-2026-112914

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2026-112914

    30-day exploitation probability 0.10%

    first.org
  • GitHub Advisory DatabasePackage advisoryGHSA-crv4-6mhj-j5jh

    filelock: SoftFileLock stale-break restore follows a swapped-in symbolic link and hard-links a file of the user running the lock into the lock directory

    github.com
  • GitLab Advisory DatabasePackage advisoryCVE-2026-112914

    When a soft-lock stale break finds that the marker (the lock file at ) it renamed aside was a live one recreated by a successor, the restore branch of break_lock_file() checks the break name with lstat (a check that reads a name without following a symbolic link) and then calls os.link(break_path, lock_file) by name. On CPython 3.12 and later on Linux (and on macOS) that call follows a symbolic li

    advisories.gitlab.com
  • NIST NVDVulnerability recordCVE-2026-112914

    filelock is a platform-independent file lock for Python. From 4.1.0 until 4.2.1, SoftFileLock can restore a stale marker by name after moving it aside, allowing another local user with rename access in a non-sticky lock directory to swap in a symbolic link and, on a runtime that

    nvd.nist.gov

References

Freshness

Last verified in this catalog Oct 23, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.