CVE-2026-22701: Lexicon · filelock Time-of-Check-Time-of-Use (TOCTOU) Symlink Vulnerability in SoftFileLock
Affects lexiconSource GCVE Database
Not known to be exploited · CVSS 5.3 Medium : upgrade to 3.23.2_3 when convenient.
Data as of 30 Oct 2026, 07:32 UTC
- Patch
- Available – fixed in 3.23.2_3
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:HExploitation evidence
Disclosed: evidence found.
CVE published 10 Jan 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by 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 3.23.2_3.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
Homebrewlexiconpkg:brew/lexiconOther threats | Affected
| Fixed in
|
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 version 3.23.2_3 that adds the O_NOFOLLOW flag to prevent symlink attacks during lock file creation. Users should upgrade to this version when possible. For critical deployments or where immediate upgrade is not feasible, users should avoid using SoftFileLock in security-sensitive contexts and prefer UnixFileLock or WindowsFileLock. Additionally, restricting filesystem permissions on lock file directories to prevent untrusted users from creating symlinks, isolating untrusted processes from lock file paths, and implementing application-level checks to verify successful lock acquisition are recommended mitigations.
Description
CVE-2026-22701 is a Time-of-Check-Time-of-Use (TOCTOU) race condition vulnerability in the SoftFileLock class of the filelock package. It allows a local attacker with permission to create symlinks to exploit a race window between permission checking and file creation, potentially causing lock operations to fail or operate on unintended files. This can lead to silent lock acquisition failures, denial of service, and resource serialization issues. The vulnerability affects applications using SoftFileLock or fallback FileLock on systems without fcntl support. A patch adding the O_NOFOLLOW flag to prevent symlink following during lock file creation is available in version 3.23.2_3. Users are advised to upgrade or apply mitigations such as avoiding SoftFileLock in sensitive contexts and restricting filesystem permissions.
References
- github.com/tox-dev/filelock/security/advisories/GHSA-qmgc-5h2g-mvrw (opens in a new tab)
- nvd.nist.gov/vuln/detail/CVE-2026-22701 (opens in a new tab)
- github.com/tox-dev/filelock/commit/255ed068bc85d1ef406e50a135e1459170dd1bf0 (opens in a new tab)
- github.com/tox-dev/filelock/commit/41b42dd2c72aecf7da83dbda5903b8087dddc4d5 (opens in a new tab)
- github.com/tox-dev/filelock (opens in a new tab)