The multicast implementation in Cisco IOS before 15.1(1)SY allows remote attackers to cause a denial of service (Route Processor crash) by sending packets at a high rate, aka Bug ID CSCts37717.
The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.