This indicates an attack attempt to exploit a Security Policy Bypass Vulnerability in Advantech WebAccess.
A remote, unauthenticated attacker could exploit this vulnerability by sending a maliciously crafted RPC request to the target server. Successful exploitation allows the attacker to execute particular system calls with user-supplied arguments on the target server.
Advantech WebAccess prior to 8.4.2
System Compromise: Remote attackers can gain control of vulnerable systems.
Apply the most recent upgrade or patch from the vendor.