An exploitable access control vulnerability exists in the data, program, and function file permissions functionality of Allen Bradley Micrologix 1400 Series B FRN 21.2 and before. A specially crafted packet can cause a read or write operation resulting in disclosure of sensitive information, modification of settings, or modification of ladder logic. An attacker can send unauthenticated packets to trigger this vulnerability.Required Keyswitch State: REMOTE or PROG Associated Fault Code: 0001 Fault Type: Non-User Description: A fault state can be triggered by setting the NVRAM/memory module user program mismatch bit (S2:9) when a memory module is NOT installed.