A denial of service vulnerability exists in Schneider Electric's MiCOM Px4x (P540 range excluded) with legacy Ethernet board, MiCOM P540D Range with Legacy Ethernet Board, and MiCOM Px4x Rejuvenated could lose network communication in case of TCP/IP open requests on port 20000 (DNP3oE) if an older TCI/IP session is still open with identical IP address and port number.