IBM Power Systems Firmware FW1060.00 through FW1060.81 is affected by a vulnerability in the service processor mailbox interface. An attacker with authenticated service-level access to the FSP can send a specially crafted mailbox message to overflow host firmware runtime attribute storage, allowing arbitrary code to be executed in the host firmware runtime. This gives the attacker full access to the managed system's memory and hardware interfaces, resulting in a confidentiality, integrity, and availability impact to the managed system.