This indicates an attack attempt against a Denial of Service vulnerability in Schneider Electric Modicon M580.
The vulnerability is caused by a design issue when the vulnerable software handles a crafted Modbus request. A remote attacker may be able to exploit this to cause a denial of service condition on the affected system, via a crafted Modbus request.
Schneider Electric Modicon M580
Schneider Electric Modicon M340
Schneider Electric Modicon Quantum
Schneider Electric Modicon Premium
Denial of Service: Remote attackers can crash vulnerable systems.
Apply the most recent upgrade or patch from the vendor.