IPsec-Tools is a port of KAME's implementation of the IPsec utilities. It contains a collection of network monitoring tools, including racoon, ping, and ping6.
The isakmp_info_recv() function in src/racoon/isakmp_inf.c does not always check that DELETE (ISAKMP_NPTYPE_D) and NOTIFY (ISAKMP_NPTYPE_N) packets are encrypted.
A remote attacker could send a specially crafted IPsec message to one of the two peers during the beginning of phase 1, resulting in the termination of the IPsec exchange.
There is no known workaround at this time.
All IPsec-Tools users should upgrade to the latest version:
# emerge --sync
# emerge --ask --oneshot --verbose ">=net-firewall/ipsec-tools-0.6.7"