Improper Neutralization of Special Elements used in a Command ('Command Injection')

Summary

An issue was discovered on D-Link DCS-1130 devices. The device provides a user with the capability of setting a SMB folder for the video clippings recorded by the device. It seems that the GET parameters passed in this request (to test if SMB credentials and hostname sent to the device work properly) result in being passed as commands to a "system" API in the function and thus result in command injection on the device. If the firmware version is dissected using binwalk tool, we obtain a cramfs-root archive which contains the filesystem set up on the device that contains all the binaries. The binary "cgibox" is the one that has the vulnerable function "sub_7EAFC" that receives the values sent by the GET request. If we open this binary in IDA-pro we will notice that this follows a ARM little endian format. The function sub_7EAFC in IDA pro is identified to be receiving the values sent in the GET request and the value set in GET parameter "user" is extracted in function sub_7E49C which is then passed to the vulnerable system API call.