This indicates an attack attempt to exploit a Buffer Overflow vulnerability in Dasan Networks GPON ONT WiFi Router.
The vulnerability is due to lack of size checking when the vulnerable software handles a maliciously crafted request. An attacker can exploit this to execute arbitrary code via crafted requests.
Dasan GPON ONT WiFi Router H640X 12.02-01121 2.77p1-1124 and 3.03p2-1146
System Compromise: Remote attackers can gain control of vulnerable systems.
Currently we are unaware of any vendor supplied patch for this issue