Cisco Catalyst 4000 series switches running CatOS 5.5.5, 6.3.5, and 7.1.2 do not always learn MAC addresses from a single initial packet, which causes unicast traffic to be broadcast across the switch and allows remote attackers to obtain sensitive network information by sniffing.

Buffer overflow in the embedded HTTP server for Cisco Catalyst switches running CatOS 5.4 through 7.3 allows remote attackers to cause a denial of service (reset) via a long HTTP request.

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).

Cisco IOS 12.2 and earlier running Cisco Discovery Protocol (CDP) allows remote attackers to cause a denial of service (memory consumption) via a flood of CDP neighbor announcements.

Cisco Catalyst 5000 series switches 6.1(2) and earlier will forward an 802.1x frame on a Spanning Tree Protocol (STP) blocked port, which causes a network storm and a denial of service.

Memory leak in Cisco Catalyst 4000, 5000, and 6000 series switches allows remote attackers to cause a denial of service via a series of failed telnet authentication attempts.

Cisco Catalyst 5.4.x allows a user to gain access to the "enable" mode without a password.