An issue was discovered in Mitsubishi Electric Automation MELSEC-Q series Ethernet interface modules QJ71E71-100 all versions QJ71E71-B5 all versions and QJ71E71-B2 all versions. The affected Ethernet interface module is connected to a MELSEC-Q PLC which may allow a remote attacker to connect to the PLC via Port 5002/TCP and cause a denial of service requiring the PLC to be reset to resume operation. This is caused by an Unrestricted Externally Accessible Lock.