gam · filelock: Symlink swap during SoftFileLock's writability check leaks whether a path exists and is writable by the lock
Affects gamSource GCVE Database
Not known to be exploited · CVSS 2.5 Low.
Data as of 9 Nov 2026, 20:05 UTC
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 9 Nov 2026.
What to do
Affected software
| Product | Affected | Fixed in |
|---|---|---|
Homebrewgampkg:brew/gamOther 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
Users should ensure that the lock directory is either sticky and world-writable with fs.protected_symlinks enabled on Linux, which blocks the symlink following in this context, or restrict directory permissions to prevent untrusted users from creating entries. Upgrading filelock beyond version 4.2.0 may include fixes or improvements; check the vendor advisory or project repository for patches. No direct patch links were provided in the advisory. If upgrading is not possible, avoid using filelock in directories where untrusted users can write or apply kernel-level protections. The vulnerability does not require additional generic mitigations.
Description
A symlink swap race condition in the SoftFileLock implementation of the filelock library allows a local user with write access to the lock directory to leak one bit of information about the existence and writability of arbitrary paths. This occurs because the writability check follows symlinks under certain conditions, revealing whether the symlink target exists and is writable by the lock user. The issue affects filelock versions 3.32.6 through 4.2.0 and is mitigated on Linux by the fs.protected_symlinks kernel setting in common sticky world-writable directories like /tmp. The vulnerability has low severity 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)