This indicates an attack attempt to exploit a Buffer Overflow Vulnerability in Advantech WebAccess.
A remote, unauthenticated attacker can exploit this vulnerability by sending a crafted request to the target system. Successful exploitation results in arbitrary code execution under the context of Administrator user. An unsuccessful attempt may result in abnormal termination of the target service.
Advantech WebAccess prior to 8.4.0
System Compromise: Remote attackers can gain control of vulnerable systems.
Apply the most recent upgrade or patch from the vendor.