Integer overflow in the SMB component in Apple Mac OS X 10.5.6 allows remote SMB servers to cause a denial of service (system shutdown) or execute arbitrary code via a crafted SMB file system that triggers a heap-based buffer overflow.
http://www.vupen.com/english/advisories/2009/0422
http://support.apple.com/kb/HT3438
http://secunia.com/advisories/33937
http://lists.apple.com/archives/security-announce/2009/Feb/msg00000.html