GHSA-9j6q-wvj5-jgjg: filelock: Symlink swap during SoftFileLock's writability check leaks whether a path exists and is writable by the lock taker

Summary

filelock versions 3.32.6 through 4.2.0 contain a symlink TOCTOU flaw in raise_on_not_writable_file(), which SoftFileLock and the locks sharing its acquire path call before each attempt. A local user who can create entries in the lock's directory can swap the lock path between a file and a symlink, so the lock user's acquire() reveals whether a chosen path exists and is writable by that user, one bit per acquire, with no content read or written. Linux fs.protected_symlinks blocks the attack in sticky world-writable directories such as /tmp, but not in 0777 directories without the sticky bit or in sticky group-writable ones.

Mitigation

The source does not state a fix yet. Check the original advisory for updates.

Affected packages in the Exposure Registry

Matched by package name and ecosystem. Each entry shows whether the package delegates to a language model and how many tracked packages depend on it.

• filelockPyPINo LLM dependency detected · 42 tracked dependents