filelock: Symlink swap during SoftFileLock's writability check leaks whether a path exists and is writable by the lock taker

影響: pip:filelock >= 3.32.6, <= 4.2.0 → 4.2.1

raise_on_not_writable_file() is the check that SoftFileLock and the locks sharing its acquire path run before every attempt. It looks at the lock path with os.lstat, so that it judges a planted symlink (a file that points at another path) by itself. When the node has no owner-write bit, it then calls os.access(filename, os.W_OK), which follows symlinks. A local user who can create entries in the lock's directory can swap the path between a mode-0466 file and a symlink to a path of their choosin…

Read on GitHub Advisory Database

On 10/29/2026, 06:08 AM, GitHub Advisory Database published "filelock: Symlink swap during SoftFileLock's writability check leaks whether a path exists and is writable by the lock taker" (type: Advisory). Severity is "Low" (low). Related technologies: Python. CVE: CVE-2026-112912.