IBM Power Systems Firmware FW1120.00, FW1110.00 through FW1110.30, FW1060.00 through FW1060.80, FW950.00 through FW950.H2, OP940.00 through OP940.a1 (Power9), and OP940.00 - OP940.81 (Power HMC) is affected by a vulnerability in the interface between the BMC/FSP and the host system. An attacker with service account or root access to the BMC/FSP can write arbitrary data to hardware control registers, allowing full control over the host system and all hosted partitions, resulting in a confidentiality, integrity, and availability impact.