An OS command injection vulnerability exists in multiple D-Link routers (confirmed on DIR-300 rev A v1.05 and DIR-615 rev D v4.13) via the authenticated toolsvct.xgi CGI endpoint. The web interface fails to properly sanitize user-supplied input in the pingIp parameter, allowing attackers with valid credentials to inject arbitrary shell commands. Exploitation enables full device compromise, including spawning a telnet daemon and establishing a root shell. The vulnerability is present in firmware versions that expose toolsvct.xgi and use the Mathopd/1.5p6 web server. No vendor patch is available, and affected models are end-of-life.