Mitsubishi MELSEC iQ-R Series PLCs with firmware 49 allow an unauthenticated attacker to halt the industrial process by sending a crafted packet over the network. This denial of service attack exposes Improper Input Validation. After halting, physical access to the PLC is required in order to restore production, and the device state is lost. This is related to R04CPU, RJ71GF11-T2, R04CPU, and RJ71GF11-T2.