This indicates an attack attempt to exploit an Insecure Deserialization Vulnerability in NetMotion Mobility Server.
The vulnerability is due to insufficient sanitizing of user supplied inputs in the application. A remote attacker may be able to exploit this to execute arbitrary code within the context of the application.
NetMotion Mobility before 11.73 and 12.x before 12.02
System Compromise: Remote attackers can gain control of vulnerable systems.
Apply the most recent upgrade or patch from the vendor.