A /shell?cmd= CSRF issue exists in the HTTPD component of NAT32 v2.2 Build 22284 devices that can be exploited for Remote Code Execution in conjunction with XSS.
https://www.exploit-db.com/exploits/44034/
http://packetstormsecurity.com/files/146402/NAT32-Build-22284-Remote-Command-Execution-CSRF.html
http://hyp3rlinx.altervista.org/advisories/NAT32-REMOTE-COMMAND-EXECUTION-CSRF-CVE-2018-6941.txt