A vulnerability has been found and corrected in dhcp:

ISC DHCP server 4.2 before 4.2.0-P2, when configured to use failover
partnerships, allows remote attackers to cause a denial of service
(communications-interrupted state and DHCP client service loss)
by connecting to a port that is only intended for a failover peer,
as demonstrated by a Nagios check_tcp process check to TCP port 520
(CVE-2010-3616).

The updated packages have been patched to correct this issue.