Totolink A7100RU Command Injection Vulnerability in CGI Handler

A command injection vulnerability has been identified in the Totolink A7100RU router, specifically in the version 7.4cu.2313_b20191024. The issue resides within the CGI handler file '/cgi-bin/cstecgi.cgi', in the 'setTelnetCfg' function. This vulnerability allows remote attackers to execute arbitrary operating system commands by manipulating the 'telnet_enabled' parameter. The injected commands are executed with root privileges, potentially compromising the router and the connected network.

Impact

Exploitation of this vulnerability allows for arbitrary command execution on the affected router with root privileges, leading to a full compromise of the device. Such access could also be used to further compromise the network to which the router is connected.

Reproduction

To reproduce this vulnerability, send a POST request to '/cgi-bin/cstecgi.cgi' with the 'telnet_enabled' parameter set to a crafted command, such as a 'wget' command pointing to a remote server. The router will execute the injected command in the background.