This indicates an attack attempt against a Denial of Service vulnerability in Cisco products.
The vulnerability is caused by an error when the vulnerable software handles a malicious http request. It allows a remote attacker to bypass the security checks of vulnerable systems via a crafted HTTP request.
Cisco routers in the AGS/MGS/CGS/AGS+, IGS, RSM, 800, ubr900, 1000, 1400, 1500, 1600, 1700, 2500, 2600, 3000, 3600, 3800, 4000, 4500, 4700, AS5200, AS5300, AS5800, 6400, 7000, 7200, ubr7200, 7500, and 12000 series.
Most recent versions of the LS1010 ATM switch.
Catalyst 6000 running IOS.
Catalyst 2900XL LAN switch running IOS.
Catalyst 1900, 2800, 2900, 3000, and 5000 series LAN switches.
Denial of Service: Remote attackers can crash vulnerable systems.
Refer to the vendor's web site for suggested workaround.