This vulnerability was discovered by Patrick DeSantis.
Talos recently discovered a vulnerability in Allen-Bradley Rockwell Automation MicroLogix 1400 Programmable Logic Controllers (PLCs) related to the default configuration that is shipped with devices running affected versions of firmware. This vulnerability is due to the presence of an undocumented SNMP community string that could be leveraged by an attacker to gain full control of affected devices and grants the ability to manipulate configuration settings, replace the firmware running on the device with attacker-controlled code, or otherwise disrupt device operations. Depending on the role of the affected PLC within an industrial control process, this could result in significant damages.
In addition to the default, documented SNMP community string of ‘public’ (read) and ‘private’ (read/write), an undocumented community string of ‘wheel’ (read/write) also exists, which enables attackers to make unauthorized device changes, such as modification of settings or conducting malicious firmware updates. It is possible that this community string allows access to other OIDs, however Talos tested specific use cases.