Cisco devices IOS 12.0 and earlier allow a remote attacker to cause a crash, or bad route updates, via malformed BGP updates with unrecognized transitive attribute.
https://exchange.xforce.ibmcloud.com/vulnerabilities/6566
http://www.securityfocus.com/bid/2733
http://www.kb.cert.org/vuls/id/106392
http://www.cisco.com/warp/public/707/ios-bgp-attr-corruption-pub.shtml