A vulnerability has been found and corrected in dhcp:

The DHCPv6 server in ISC DHCP 4.0.x and 4.1.x before 4.1.2-P1, 4.0-ESV
and 4.1-ESV before 4.1-ESV-R1, and 4.2.x before 4.2.1b1 allows remote
attackers to cause a denial of service (assertion failure and daemon
crash) by sending a message over IPv6 for a declined and abandoned
address (CVE-2011-0413).

The updated packages have been patched to correct this issue.