A flaw was found in GNU nano's multi-buffer error message handling. When a user opens multiple files at startup and one triggers an ALERT-level error, a specially crafted filename containing printf format specifiers can be reinterpreted. This format string vulnerability may allow an attacker to achieve stack information disclosure, cause a denial of service (crash), or potentially perform arbitrary memory writes.
Users should avoid opening untrusted files with GNU nano, especially those with filenames containing printf format specifiers (e.g., %s, %p, %n). This operational control helps prevent the exploitation of the format string vulnerability, which relies on specific filename content and error conditions during multi-buffer usage.