** UNSUPPORTED WHEN ASSIGNED ** The remote code execution vulnerability in the CGI program “file_upload-cgi” in Zyxel NAS326 firmware versions before V5.21(AAZF.17)C0 and NAS542 firmware versions before V5.21(ABAG.14)C0 could allow an unauthenticated attacker to execute arbitrary code by uploading a crafted configuration file to a vulnerable device.
https://outpost24.com/blog/zyxel-nas-critical-vulnerabilities/