The vulnerability is an integer overflow in the interface between the BMC/FSP and the host system of IBM Power Systems Firmware. It allows an attacker who has service account or root level access to the BMC/FSP to read from or write to arbitrary memory on the host system. This gives complete control over the host and any hosted partitions, effectively compromising confidentiality, integrity and availability of the entire system.

Affected products are IBM Power Systems Firmware versions FW1120.00 up to FW1120.00, FW1110.00 through FW1110.30, FW1060.00 through FW1060.80, FW950.00 through FW950.H2, OP940.00 through OP940.a1 on Power9, and OP940.00 through OP940.81 on the Power Hardware Management Console (HMC). Specific firmware updates to remediate the issue are FW1110.31(1110_155) or newer for Power 11, FW1120.01(1120_190) or newer for Power 11 and Power 10, FW1060.81(1060_184) or newer for Power 9, FW950.H3(950_230) or newer for Power 9, OP940.a2 or newer for AC922, and OP940.82 or newer for the Power HMC. These updates apply to the wide list of Power System models enumerated in the advisory.

The vulnerability has a CVSS score of 8.2, indicating a high severity. EPSS data is not available but the lack of a KEV listing suggests that a known exploit is not publicly documented as of the last report. An attacker would need access to the BMC/FSP, which typically requires having an account with service or root privileges, or physical access to management interfaces. Once the preconditions are met, the overflow can be triggered to hijack system memory, leading to full host compromise. Given the high impact and the ease of exploitation once the attacker's access is established, the risk is considered significant.