Cisco Internetwork Operating System (IOS) 12.0S through 12.3T attempts to process SNMP solicited operations on improper ports (UDP 162 and a randomly chosen UDP port), which allows remote attackers to cause a denial of service (device reload and memory corruption).

Multiple vulnerabilities in the H.323 protocol implementation for Cisco IOS 11.3T through 12.2T allow remote attackers to cause a denial of service and possibly execute arbitrary code, as demonstrated by the NISCC/OUSPG PROTOS test suite for the H.225 protocol.

Cisco IOS 12.0 through 12.2, when IP routing is disabled, accepts false ICMP redirect messages, which allows remote attackers to cause a denial of service (network routing modification).

Cisco IOS 12.2 and earlier generates a "% Login invalid" message instead of prompting for a password when an invalid username is provided, which allows remote attackers to identify valid usernames on the system and conduct brute force password guessing, as reported for the Aironet Bridge.

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.

The Service Assurance Agent (SAA) in Cisco IOS 12.0 through 12.2, aka Response Time Reporter (RTR), allows remote attackers to cause a denial of service (crash) via malformed RTR packets to port 1967.

Buffer overflow in Cisco IOS 11.2.x to 12.0.x allows remote attackers to cause a denial of service and possibly execute commands via a large number of OSPF neighbor announcements.

Cisco IOS 11.2.x and 12.0.x does not limit the size of its redirect table, which allows remote attackers to cause a denial of service (memory consumption) via spoofed ICMP redirect packets to the router.

Extended Interior Gateway Routing Protocol (EIGRP), as implemented in Cisco IOS 11.3 through 12.2 and other products, allows remote attackers to cause a denial of service (flood) by sending a large number of spoofed EIGRP neighbor announcements, which results in an ARP storm on the local network.

Cisco IOS 11.1 through 12.2, when HSRP support is not enabled, allows remote attackers to cause a denial of service (CPU consumption) via randomly sized UDP packets to the Hot Standby Routing Protocol (HSRP) port 1985.