Unspecified vulnerability in the Multicast Virtual Private Network (MVPN) implementation in Cisco IOS 12.0, 12.2, 12.3, and 12.4 allows remote attackers to create "extra multicast states on the core routers" via a crafted Multicast Distribution Tree (MDT) Data Join message.

More... (http://nvd.nist.gov/nvd.cfm?cvename=CVE-2008-1156)