Cisco IOS before 15.3(1)T, when media flow-around is not used, allows remote attackers to cause a denial of service (media loops and stack memory corruption) via VoIP traffic, aka Bug ID CSCub45809.
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.