Cisco Hot Standby Routing Protocol (HSRP) allows local attackers to cause a denial of service by spoofing HSRP packets.
https://exchange.xforce.ibmcloud.com/vulnerabilities/6497
http://www.cisco.com/networkers/nw00/pres/2402.pdf
http://archives.neohapsis.com/archives/bugtraq/2001-05/0035.html