Memory leak in Cisco IOS 15.1 through 15.4 and IOS XE 3.4.xS, 3.5.xS, 3.6.xS, and 3.7.xS before 3.7.6S; 3.8.xS, 3.9.xS, and 3.10.xS before 3.10.1S; and 3.11.xS before 3.12S allows remote attackers to cause a denial of service (memory consumption or device reload) via malformed DHCPv6 packets, aka Bug ID CSCum90081.