This indicates an attack attempt to exploit a Denial of Service vulnerability in Apache Tomcat.
The vulnerability is due to an error when vulnerable software handles a crafted HTTP chunked Transfer coding. A remote attacker may be able to exploit this to cause a denial of service condition on the affected system.
Apache HTTP Server 64-bit 1.3.41 and prior
Denial of Service: Remote attackers can crash vulnerable systems or services
Apply the most recent upgrade or patch from the vendor.