CWE-78:Improper Neutralization of Special Elements used in an OS Command(‘OS Command Injection’) ZyXEL NAS devices achieve authentication by using the weblogin.cgi CGI executable. This program fails to properly sanitize the username parameter that is passed to it. If the username parameter contains certain characters,it can allow command injection with the privileges of the web server that runs on the ZyXEL device. Although the web server does not run as the root user,ZyXEL devices include a setuid utility that can be leveraged to run any command with root privileges. As such,it should be assumed that exploitation of this vulnerability can lead to remote code execution with root privileges. Exploit code for this vulnerability is available on the internet. For this reason,we have created a PoC exploit that has the ability to power down affected ZyXEL devices.