Can someone please tell me how to patch my Linux box?

Trivial. Every MTA worth its salt, and that includes most available for Linux, knows how to deal with a .mailcap file. Even browsers like Netscape know how to deal with a .mailcap file. It's very easy to configure your .mailcap file so it fires up perl whenever you receive an email or webpage with MIME type application/perl. Or fire up another turing complete language interpreter for another MIME type. Does your mailer conveniently fire up a PostScript viewer when you open up a PostScript attachment? PostScript is a powerful language, are you sure your PostScript interpreter doesn't have security holes?

Abigail