cisco-sa-20011115-ios-arp-overwrite · NA · Published · Updated
It is possible to send an Address Resolution Protocol (ARP) packet on a local broadcast interface (for example, Ethernet, cable, Token Ring, FDDI) which could cause a router or switch running specific versions of Cisco IOS® Software Release to stop sending and receiving ARP packets on the local router interface. This will in a short time cause the router and local hosts to be unable to send packets to each other. ARP packets received by the router for the router's own interface address but a different Media Access Control (MAC) address will overwrite the router's MAC address in the ARP table with the one from the received ARP packet. This was demonstrated to attendees of the Black Hat conference and should be considered to be public knowledge. This attack is only successful against devices on the segment local to the attacker or attacking host. This vulnerability is documented in Cisco Bug ID CSCdu81936, and a workaround is available. The complete notice will be available at https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20011115-ios-arp-overwrite.