This indicates an attack attempt to exploit a Denial of Service Vulnerability in Rockwell Automation RSLinx Classic.
The vulnerability occurs while processing network request to Ethernet/IP server. A remote, unauthenticated attacker can exploit this vulnerability by sending sequence of specially crafted packet to the vulnerable service. Successful exploitation could lead to denial-of-service conditions in the target server.
Rockwell Automation RSLinx Classic 4.12.00 and prior
Denial of Service: Remote attackers can crash vulnerable systems.
Rockwell Automation has not released an advisory or patch regarding this vulnerability.