CVE-2026-18821: CWE-787 Out-of-bounds Write in IBM PowerVM Hypervisor

IBM PowerVM Hypervisor firmware versions FW1120.00, FW1110.00 through FW1110.30, FW1060.00 through FW1060.80, and FW950.00 through FW950.H2 are affected by an out-of-bounds write vulnerability (CWE-787) in the partition firmware during network boot. An unauthenticated attacker on the same network segment as a partition performing network boot can send a malformed packet that triggers arbitrary code execution within that partition's firmware. This vulnerability compromises the confidentiality, integrity, and availability of the affected partition and any software subsequently loaded by it. Other partitions and the overall managed system are not impacted by this vulnerability.

The vulnerability allows an unauthenticated attacker on the same network as a partition undergoing network boot to execute arbitrary code in the partition firmware. This results in a full compromise of the affected partition's confidentiality, integrity, and availability. However, the attack does not affect other partitions or the managed system as a whole.

No patch or official fix information is provided in the available data. Patch status is not yet confirmed — check the IBM vendor advisory for current remediation guidance. Until a fix is available, avoid performing network boots on partitions in untrusted network environments or isolate network boot traffic to trusted networks only.