CVE-2026-112912GHSA-9j6q-wvj5-jgjg
filelock: Symlink swap during SoftFileLock's writability check leaks whether a path exists and is writable by the lock taker
tox-dev filelock
CVSS
2.5LowExploitationPublic exploit codeCISA's assessment says proof of concept code is public, assessed 20 Oct 2026. Not in the KEV catalogCISA via CVE List
Exploit odds (EPSS)0.21%Chance of exploitation activity in the next 30 days, higher than 11% of CVEs. Scored 23 Oct 2026FIRST EPSS
What fixes it
- 4.2.1filelock, pipGitHub
A fixed version on one release line is not the upgrade target for every line. Check your exact version and any vendor backports.
Description
filelock is a platform-independent file lock for Python. From 3.32.6 until 4.2.1, SoftFileLock can follow a swapped symbolic link during the conditional os.access writability check for a node without its owner-write bit, allowing another local user on a platform and directory configuration that follows the link to infer whether a chosen path exists and is writable from the observable acquisition result. This issue is fixed in version 4.2.1.
Text from CVE List
Affected versions 2
- filelockaffected: >= 3.32.6, < 4.2.1CVE List
- filelock, pip>= 3.32.6, <= 4.2.0GitHub