IPSec when used with VPN networks in Mac OS X 10.4 through 10.4.5 allows remote attackers to cause a denial of service (application crash) via unspecified vectors involving the "incorrect handling of error conditions".
https://exchange.xforce.ibmcloud.com/vulnerabilities/25025
http://www.vupen.com/english/advisories/2006/0791
http://www.us-cert.gov/cas/techalerts/TA06-062A.html
http://www.securityfocus.com/bid/16907
http://secunia.com/advisories/19064
http://lists.apple.com/archives/security-announce/2006/Mar/msg00000.html