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CVE-2026-112939VulnerabilityPublished

poetry · filelock: SoftFileLock removes a live holder's marker when another user forges the PID in a writable marker

Affects poetrySource GCVE Database

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Authoritative record:CVE-2026-112939· Medium 4.7

Not known to be exploited · CVSS 4.7 Medium : upgrade to 2.5.1_1 when convenient.

Data as of 30 Oct 2026, 08:29 UTC

CVSS 3.1 base score
4.7Medium
How severe the flaw is on the 0–10 CVSS scale.
Patch
Available – fixed in 2.5.1_1
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:N

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 20 Oct 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 29 Oct 2026.

What to do

Upgrade poetry to 2.5.1_1.

Affected software

ProductAffectedFixed in
Homebrewpoetrypkg:brew/poetryOther threatsAffected
  • >=2.3.2_1 <2.5.1_1
Fixed in
  • 2.5.1_1

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

A fix is available in filelock version 2.5.1_1. Users should upgrade to this version or later to resolve the vulnerability. Until patched, avoid setting group or other write permissions on lock marker files and ensure directories containing lock files are sticky or otherwise restrict marker file removal. Do not rely on soft file locks in environments where untrusted local users can write marker files.

Description

A vulnerability in filelock versions 3.22.0 through 4.2.0 allows a local user with write access to a lock marker file (but not removal rights) to forge the process ID in the marker. This causes the lock to be incorrectly considered stale, enabling two processes to simultaneously hold the lock and write to the protected resource without error. The issue arises when the marker file is group- or other-writable, typically due to permissive file modes or umask settings in sticky or restricted directories. The vulnerability has medium severity with a CVSS score of 4.7.

References

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