This indicates an attack attempt against a buffer-overflow vulnerability in HP OpenView Network Node Manager (OV NNM).
The vulnerability is caused by an error when the vulnerable software handles a specially crafted HTTP request. It allows a remote attacker to execute arbitrary code.
HP OpenView Network Node Manager 7.53
HP OpenView Network Node Manager 7.51
System Compromise: Remote attackers can gain control of vulnerable systems.
Apply the patch supplied by the vendor: