Vulnerability in Cisco IOS 11.1CC and 11.1CT with distributed fast switching (DFS) enabled allows remote attackers to bypass certain access control lists when the router switches traffic from a DFS-enabled interface to an interface that does not have DFS enabled, as described by Cisco bug CSCdk35564.

Attackers can crash a Cisco IOS router or device, provided they can get to an interactive prompt (such as a login). This applies to some IOS 9.x, 10.x, and 11.x releases.

Some classic Cisco IOS devices have a vulnerability in the PPP CHAP authentication to establish unauthorized PPP connections.