An attacker with network access to the affected PLC (CJ-series and CS-series PLCs, all versions) may use a network protocol to read and write files on the PLC internal memory and memory card.

Omron CJ1M unit v4.0 and prior has improper access controls on the memory region where the UM password is stored. If an adversary issues a PROGRAM AREA WRITE command to a specific memory region, they could overwrite the password. This may lead to disabling UM protections or setting a non-ASCII password (non-keyboard characters) and preventing an engineer from viewing or modifying the user program.