This indicates an attack attempt against a Buffer Overflow vulnerability in the Advantech WebAccess.
The vulnerability is due to insufficient sanitizing of inputs when the vulnerable application handles a maliciously crafted request. An attacker can exploit this by sending maliciously crafted requests to the vulnerable application and execute arbitrary code within the context of the affected machine.
Advantech WebAccess 8.1 and prior
System Compromise: Remote attackers can gain control of vulnerable systems.
Currently we are unaware of any vendor supplied patch for this issue