CVE-2026-16661 Power System Integer Overflow

High 8.2 Published 19 Aug 2026 Updated 22 Aug 2026

An attacker with authenticated service-level access can exploit an integer overflow in the service processor mailbox to execute arbitrary code in the host firmware.

Exploited in the wild: Not known
Login needed: An administrator
Attackable: Local or same network only
Victim action needed: Not needed
Fix: None listed

What is CVE-2026-16661?

CVE-2026-16661 is a high-severity vulnerability in IBM PowerVM Hypervisor, published on 19 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.

Official description

IBM PowerVM Hypervisor FW1120.00, FW1110.00 through FW1110.30, FW1060.00 through FW1060.80, and FW950.00 through FW950.H2 is affected by a vulnerability in the service processor mailbox interface. An attacker with authenticated service-level access to the FSP can exploit this vulnerability, allowing arbitrary code to be executed in the host firmware runtime, giving full control over the managed system, resulting in a confidentiality, integrity, and availability impact to the managed system.

Weakness: CWE-190

Which versions are affected by CVE-2026-16661?

It affects 26 products.

Products include Ibm Power System E1050 \(9043-Mrx\) Firmware, Ibm Power System E1080 \(9080-Hex\) Firmware, Ibm Power System E1150 \(9043-Mru\) Firmware, Ibm Power System E1180 \(9080-Heu\) Firmware, Ibm Power System E950 \(9040-Mr9\) Firmware, Ibm Power System E980 \(9080-M9s\) Firmware and 20 more.

How do I fix CVE-2026-16661?

No fix has been published for CVE-2026-16661 yet. Limit exposure of the affected software until one is available.

Is CVE-2026-16661 being exploited?

There is no known exploitation of CVE-2026-16661 in the wild and no public exploit code.

Sources

Also known as GHSA-xx9m-vc9m-c7wp.