virtualenvwrapper · filelock: Symlink swap during SoftFileLock's writability check leaks whether a path exists and is writable by the lock
Affects virtualenvwrapperSource GCVE Database
Not known to be exploited · CVSS 2.5 Low : upgrade to 6.1.1_4 when convenient.
Data as of 30 Oct 2026, 06:59 UTC
- EPSS
- 0.2% chance of exploitation in 30 days – higher than 11% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in 6.1.1_4
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:NExploitation evidence
Disclosed: evidence found.
CVE published 20 Oct 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 virtualenvwrapper to 6.1.1_4.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
Homebrewvirtualenvwrapperpkg:brew/virtualenvwrapperOther 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 fix is available in virtualenvwrapper version 6.1.1_4. Users should upgrade to this version or later to remediate the vulnerability. On Linux systems, enabling the fs.protected_symlinks kernel setting and using sticky world-writable directories (e.g., /tmp) for lock files can mitigate the issue by preventing symlink following in these directories. No additional action is required if these mitigations are in place. The vulnerability does not affect Windows or BSD/macOS platforms due to differing symlink behavior.
Description
A symlink swap race condition in the SoftFileLock implementation allows a local user with write access to the lock directory to leak one bit of information about whether a path exists and is writable by the lock user. This occurs because the writability check follows symlinks after an lstat call, enabling a time-of-check to time-of-use (TOCTOU) leak. 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 existence and writability of a chosen path, with no integrity or availability effects. The vulnerability is rated low severity with a CVSS score of 2.5 due to high attack complexity and limited information leakage.
References
- github.com/tox-dev/filelock/security/advisories/GHSA-9j6q-wvj5-jgjg (opens in a new tab)
- nvd.nist.gov/vuln/detail/CVE-2026-112912 (opens in a new tab)
- github.com/tox-dev/filelock/pull/835 (opens in a new tab)
- github.com/tox-dev/filelock/commit/e1e825b1992f69fb6b346dc395d5ae4893536c0a (opens in a new tab)
- github.com/tox-dev/filelock (opens in a new tab)
- github.com/tox-dev/filelock/releases/tag/4.2.1 (opens in a new tab)