The T1/E1 driver-queue functionality in Cisco IOS 12.2 and 15.0 through 15.3, when an HDLC32 driver is used, allows remote attackers to cause a denial of service (interface queue wedge) via bursty network traffic, aka Bug ID CSCub67465.
http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20130925-wedge