Cisco IOS allows remote attackers to cause a denial of service (crash) via a crafted IPv6 Type 0 Routing header.

The TCL shell in Cisco IOS 12.2(14)S before 12.2(14)S16, 12.2(18)S before 12.2(18)S11, and certain other releases before 25 January 2006 does not perform Authentication, Authorization, and Accounting (AAA) command authorization checks, which may allow local users to execute IOS EXEC commands that were prohibited via the AAA configuration, aka Bug ID CSCeh73049.

Buffer overflow in Firewall Authentication Proxy for FTP and/or Telnet Sessions for Cisco IOS 12.2ZH and 12.2ZL, 12.3 and 12.3T, and 12.4 and 12.4T allows remote attackers to cause a denial of service and possibly execute arbitrary code via crafted user authentication credentials.

Cisco IOS 12.0 through 12.4 and IOS XR before 3.2, with IPv6 enabled, allows remote attackers on a local network segment to cause a denial of service (device reload) and possibly execute arbitrary code via a crafted IPv6 packet.

Cisco IOS 12.2T through 12.4 allows remote attackers to bypass Authentication, Authorization, and Accounting (AAA) RADIUS authentication, if the fallback method is set to none, via a long username.

Secure Shell (SSH) 2 in Cisco IOS 12.0 through 12.3 allows remote attackers to cause a denial of service (device reload) (1) via a username that contains a domain name when using a TACACS+ server to authenticate, (2) when a new SSH session is in the login phase and a currently logged in user issues a send command, or (3) when IOS is logging messages and an SSH session is terminated while the server is sending data.

Cisco IOS 12.0S through 12.3YH allows remote attackers to cause a denial of service (device restart) via a crafted IPv6 packet.

Cisco IOS 12.0 through 12.3YL, with BGP enabled and running the bgp log-neighbor-changes command, allows remote attackers to cause a denial of service (device reload) via a malformed BGP packet.

Cisco IOS 11.x and 12.0 through 12.2 allows remote attackers to cause a denial of service (traffic block) by sending a particular sequence of IPv4 packets to an interface on the device, causing the input queue on that interface to be marked as full.