Screen Sharing in Apple Mac OS X 10.5.8 allows remote VNC servers to execute arbitrary code or cause a denial of service (memory corruption and application crash) via unspecified vectors.
http://www.vupen.com/english/advisories/2009/3184
http://www.securityfocus.com/bid/36956
http://support.apple.com/kb/HT3937
http://lists.apple.com/archives/security-announce/2009/Nov/msg00000.html