filelock CVE-2026-112912

Exploitation requires all of the following: a local account on the same host as the victim (AV:L, PR:L); the victim using filelock's SoftFileLock between 3.32.6 and 4.2.1; a lock-path node whose owner-write bit is unset, triggering the conditional os.access() writability check; a platform and directory configuration in which os.access follows symbolic links; and the attacker's ability to swap a symlink in at the lock path and win the TOCTOU race (AC:H). Limiting factors: it is local-only (not remotely reachable), yields only an existence/writability inference about an attacker-chosen path rather than content disclosure or write access, and is neutralized on platforms/configurations that do not follow the swapped link.

This is a genuinely low-priority issue, and the available signals agree rather than conflict. The CVSS 3.1 vector (AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N, base 2.5) describes a local, high-complexity, authenticated flaw with only limited confidentiality impact and no integrity or availability effect - consistent with the description, which frames the outcome as an information-inference primitive (learning whether a chosen path exists and is writable), not code execution or data theft. No EPSS score, KEV listing, or POC was provided in the intelligence; by rule this is 'no public exploit identified at time of analysis,' and the symlink TOCTOU nature plus AC:H means reliable exploitation requires winning a race on a specific platform/directory configuration. There is no conflict among signals here: low CVSS, no exploitation evidence, and a narrow local info-leak primitive all point the same direction. The main caveat is reach: filelock is an extremely common transitive Python dependency, so while per-instance risk is low, the affected code is present in a very large number of environments - patch during routine dependency maintenance rather than as an emergency.

A local attacker with their own account on a shared multi-user host swaps a symbolic link in at a SoftFileLock lock path for a file whose owner-write bit is unset, timing it against a victim process's os.access() writability check. By observing whether the victim's lock acquisition succeeds, the attacker infers whether an attacker-chosen target path exists and is writable by the victim. No public exploit code was identified, and the AC:H race plus required local account make opportunistic exploitation unlikely.