Isn't this irrelevant since no one is 1) using CGI on Macs and 2) no one is using a Mac as a server?
2) People do use Macs as servers. It's unwise, clearly, but it is done. https://www.apple.com/osx/server/
3) OSX server is setup for CGI by default, all you have to do is throw some scripts in the right directory.
https://www.trustedsec.com/september-2014/shellshock-dhcp-rc...
The DHCP vector was demonstrated to be an issue with various Linux distributions.