Netis AC1200 Router NC21 V4.0.1.4296 contains a hard-coded root credential stored in /etc/shadow.sample. The password for the root account is set to the trivially weak value root, allowing an attacker with access to the device to authenticate as root and gain full control of the underlying operating system.

Netis AC1200 Router NC21 V4.0.1.4296 is vulnerable to unauthenticated command injection via the /cgi-bin/skkset.cgi endpoint. The password and newpwdconfirm POST parameters are passed directly to the underlying OS shell without sanitization. An attacker can inject arbitrary shell commands by wrapping them in backticks () and encoding them in base64. Because the endpoint requires no authentication, any device on the LAN can achieve full Remote Code Execution on the router's operating system with a single HTTP POST request.