Question about CGI scripts

Is it possible to have a cgi script run arbitrary commands? For example have the script run "aumix -v+5" to increase the volume on the machine it's running on.

The idea is to have a web page on a web sever running on my linux box that I can use to control the volume, play/pause music, etc. Then I could use my phone to navigate to that page and sort of use it as a remote for the PC. The phone doesn't have wifi so I can't just use ssh to log into my comp and do it that way.

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Another question. thttpd used the user www-data which I assume is basically the same as nobody. But why is it that it can run programs like cat,echo,date, & mpc but not aumix? The permissions are the same for all of them. What is it about aumix the is different? Would the user www-data need to be part of the audio group?