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CVE-2026-112912VulnerabilityPublished

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

Affects lexiconSource 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 3.25.2_5 when convenient.

Data as of 30 Oct 2026, 07:32 UTC

CVSS 3.1 base score
2.5Low
How severe the flaw is on the 0–10 CVSS scale.
Patch
Available – fixed in 3.25.2_5
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 lexicon to 3.25.2_5.

Affected software

ProductAffectedFixed in
Homebrewlexiconpkg:brew/lexiconOther threatsAffected
  • >=3.25.2_3 <3.25.2_5
Fixed in
  • 3.25.2_5

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 3.25.2_5 that fixes this vulnerability. Users should upgrade to this version or later. On Linux systems, enabling the fs.protected_symlinks kernel setting (which is typically enabled by default) helps block this attack in sticky world-writable directories such as /tmp. Avoid using lock directories with 0777 permissions without the sticky bit or sticky group-writable directories to reduce exposure. No other specific mitigation is required as the vulnerability does not allow modification or denial of service.

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) race condition. The vulnerability affects filelock versions 3.32.6 through 4.2.0 and is mitigated on Linux by the fs.protected_symlinks kernel setting in sticky world-writable directories like /tmp. The impact is limited to leaking a single bit of information per lock acquire attempt, with no integrity or availability impact. The vulnerability requires local access, the ability to create entries in the lock directory, and a race condition timing that is complex to achieve.

References

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