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.

Cisco IOS 12.2 through 12.4 before 20060920, as used by Cisco IAD2430, IAD2431, and IAD2432 Integrated Access Devices, the VG224 Analog Phone Gateway, and the MWR 1900 and 1941 Mobile Wireless Edge Routers, is incorrectly identified as supporting DOCSIS, which allows remote attackers to gain read-write access via a hard-coded cable-docsis community string and read or modify arbitrary SNMP variables.

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.

The HTTP server in Cisco IOS 12.0 through 12.1 allows local users to cause a denial of service (crash and reload) via a URL containing a "?/" string.

Heap-based buffer overflow in the VLAN Trunking Protocol (VTP) feature in Cisco IOS 12.1(19) allows remote attackers to execute arbitrary code via a long VLAN name in a VTP type 2 summary advertisement.

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.

The VLAN Trunking Protocol (VTP) feature in Cisco IOS 12.1(19) and CatOS allows remote attackers to cause a denial of service by sending a VTP update with a revision value of 0x7FFFFFFF, which is incremented to 0x80000000 and is interpreted as a negative number in a signed context.

The VLAN Trunking Protocol (VTP) feature in Cisco IOS 12.1(19) allows remote attackers to cause a denial of service by sending a VTP version 1 summary frame with a VTP version field value of 2.

In Cisco IOS 10.3, with the tacacs-ds or tacacs keyword, an extended IP access control list could bypass filtering.

The Cisco Optical Service Module (OSM) for the Catalyst 6500 and 7600 series running Cisco IOS 12.1(8)E through 12.1(13.4)E allows remote attackers to cause a denial of service (hang) via a malformed packet.

Cisco IOS 12.0, 12.1, and 12.2, when GRE IP tunneling is used and the RFC2784 compliance fixes are missing, does not verify the offset field of a GRE packet during decapsulation, which leads to an integer overflow that references data from incorrect memory locations, which allows remote attackers to inject crafted packets into the routing queue, possibly bypassing intended router ACLs.

Cisco Gigabit Switch Routers (GSR) with Fast Ethernet / Gigabit Ethernet cards, from IOS versions 11.2(15)GS1A up to 11.2(19)GS0.2 and some versions of 12.0, do not properly handle line card failures, which allows remote attackers to bypass ACLs or force the interface to stop forwarding packets.

Cisco PIX firewall and CBAC IP fragmentation attack results in a denial of service.

Cisco Gigabit Switch routers running IOS allow remote attackers to forward unauthorized packets due to improper handling of the "established" keyword in an access list.

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

Internet Key Exchange (IKE) version 1 protocol, as implemented on Cisco IOS, VPN 3000 Concentrators, and PIX firewalls, allows remote attackers to cause a denial of service (resource exhaustion) via a flood of IKE Phase-1 packets that exceed the session expiration rate. NOTE: it has been argued that this is due to a design weakness of the IKE version 1 protocol, in which case other vendors and implementations would also be affected.

Cisco IOS 12.0 and other versions can be crashed by malicious UDP packets to the syslog port.

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.

The web interface on Cisco IOS 12.3(8)JA and 12.3(8)JA1, as used on the Cisco Wireless Access Point and Wireless Bridge, reconfigures itself when it is changed to use the "Local User List Only (Individual Passwords)" setting, which removes all security and password configurations and allows remote attackers to access the system.

The IOS HTTP service in Cisco routers and switches running IOS 11.1 through 12.1 allows remote attackers to cause a denial of service by requesting a URL that contains a %% string.