We seem to hear much less about Apple software security vulnerabilities than we do for Windows and IE, but that does not mean that Macs don't have their problems too. For example, several vulnerabilities have been found in Darwin, the implementation of Unix that underlies Mac OS X. Affecting versions of Mac OS X up to and including 10.3.4, the flaw concerns the operating system's SearchFS function and 'at' command. There are also several potential kernel memory overflows to watch out for as well. Immunity, the company who discovered these problems, is working on producing reliable exploits for them, as part of its security testing program. The problems, however, don't appear to be too severe.
Immunity emphasized that for the majority of customers, the bugs posed little threat. Instead they are most likely to affect systems with multiple users accessing the system remotely.