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.
https://www.isc.org/software/dhcp/advisories/cve-2010-3616
https://lists.isc.org/pipermail/dhcp-users/2010-December/012368.html
http://www.vupen.com/english/advisories/2011/0052
http://www.vupen.com/english/advisories/2010/3208
http://www.securitytracker.com/id?1024862
http://www.securityfocus.com/bid/45360
http://www.mandriva.com/security/advisories?name=MDVSA-2011:001
http://www.kb.cert.org/vuls/id/159528
http://secunia.com/advisories/42682
http://secunia.com/advisories/42618
http://lists.fedoraproject.org/pipermail/package-announce/2010-December/052329.html