A Time-of-Check Time-of-Use (TOCTOU) race condition was found in GNU sed. When the -i (in-place) and --follow-symlinks options are used together, sed resolves the symlink but reopens the path for writing. An attacker with write access to the directory containing the symlink can swap it between the check and the open operations. If a privileged user executes sed in this manner on a path influenced by the attacker, it can lead to arbitrary file overwrites and potential privilege escalation.