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CVE-2026-112912VulnerabilityPublished

poetry · filelock: Symlink swap during SoftFileLock's writability check leaks whether a path exists and is writable by the lock

Affects poetrySource GCVE Database

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Authoritative record:CVE-2026-112912· Low 2.5

Not known to be exploited · CVSS 2.5 Low : upgrade to 2.5.1_1 when convenient.

Data as of 30 Oct 2026, 08:30 UTC

CVSS 3.1 base score
2.5Low
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:L/I:N/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
  • >=2.5.0 <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 patch is available in filelock version 2.5.1_1 that fixes this vulnerability. Users should upgrade to this version or later. On Linux systems, enabling the fs.protected_symlinks kernel setting and using sticky bit on world-writable directories (e.g., /tmp) helps mitigate the issue. No other specific mitigations are required as the vulnerability is low severity and requires local access and a race condition.

Description

A symlink swap vulnerability in filelock's SoftFileLock writability check allows a local user to leak one bit of information about whether a path exists and is writable by the lock user. This occurs because the check uses os.lstat followed by os.access, which follows symlinks, enabling a time-of-check to time-of-use (TOCTOU) leak. The vulnerability affects filelock versions 3.32.6 through 4.2.0 and requires the attacker to create entries in the lock directory and race the lock user's acquire calls. Linux's fs.protected_symlinks kernel setting mitigates this in sticky world-writable directories like /tmp, but not in others. The impact is limited to a low-severity confidentiality leak of a single bit per acquire attempt. A fix is available in filelock version 2.5.1_1.

References

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