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.

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 12.2(15) and earlier allows remote attackers to cause a denial of service (refused VTY (virtual terminal) connections), via a crafted TCP connection to the Telnet or reverse Telnet port.

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.

Cisco IOS 12.0 through 12.2, when supporting SSH, allows remote attackers to cause a denial of service (CPU consumption) via a large packet that was designed to exploit the SSH CRC32 attack detection overflow (CVE-2001-0144).

Buffer overflow in Cisco TACACS+ tac_plus server allows remote attackers to cause a denial of service via a malformed packet with a long length field.