This indicates an attack attempt against a Denial of Service vulnerability in Cisco Catalyst switch.
The vulnerability is caused by an error when the vulnerable software handles overly long http requests. It allows a remote attacker to crash vulnerable systems via sending a crafted HTTP request.
Cisco CatOS 7.4
Cisco CatOS 7.3
Cisco CatOS 6.1 (2)
Cisco CatOS 6.1
Cisco CatOS 5.5 (13a)
Cisco CatOS 5.5
Cisco CatOS 5.4
System Compromise: Remote attackers can crash vulnerable systems.
Refer to the vendor's web site for suggested workaround.