A command injection vulnerability exists in the D-Link DIR-882 Router firmware DIR882A1_FW102B02 within the prog.cgi and rc binaries. The sub_4438A4 function in prog.cgi stores user-supplied DDNS parameters (ServerAddress and Hostname) in NVRAM via nvram_safe_set. These values are later retrieved in the start_DDNS_ipv4 function of rc using nvram_safe_get and concatenated into DDNS shell commands executed via twsystem() without proper sanitization. Partial string comparison is performed but is insufficient to prevent command injection. An unauthenticated remote attacker can exploit this vulnerability to execute arbitrary commands on the device through specially crafted HTTP requests to the routers web interface.
The product constructs all or part of a command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended command when it is sent to a downstream component.
Many protocols and products have their own custom command language. While OS or shell command strings are frequently discovered and targeted, developers may not realize that these other command languages might also be vulnerable to attacks.