CVE-2026-18821: Power System Out-of-bounds Write

Severity: high (CVSS 8.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-08-19 · updated 2026-08-25
Weakness: CWE-787

Description

IBM PowerVM Hypervisor FW1120.00, FW1110.00 through FW1110.30, FW1060.00 through FW1060.80, and FW950.00 through FW950.H2 Power Systems Firmware is affected by a vulnerability in partition firmware during network boot. An unauthenticated attacker on the same network as a partition undergoing network boot can send a malformed packet, allowing arbitrary code to be executed in the partition firmware and compromising everything subsequently loaded by that partition. Other partitions and the managed system are not affected. Only partitions actively performing a network boot are affected, resulting in a confidentiality, integrity, and availability impact.

Affected products

IBM Power System E1050 (9043-Mrx) Firmware: from fw1060.00 before fw1060.81 — fixed in fw1060.81
IBM Power System E1080 (9080-Hex) Firmware: from fw1060.00 before fw1060.81 — fixed in fw1060.81
IBM Power System E1150 (9043-Mru) Firmware: from fw1110.00 before fw1110.31; fw1120.00 — fixed in fw1110.31
IBM Power System E1180 (9080-Heu) Firmware: from fw1110.00 before fw1110.31; fw1120.00 — fixed in fw1110.31
IBM Power System E950 (9040-Mr9) Firmware: from fw950.00 before fw950.h3 — fixed in fw950.h3
IBM Power System E980 (9080-M9S) Firmware: from fw950.00 before fw950.h3 — fixed in fw950.h3
IBM Power System H922 (9223-22S) Firmware: from fw950.00 before fw950.h3 — fixed in fw950.h3
IBM Power System H924 (9223-42S) Firmware: from fw950.00 before fw950.h3 — fixed in fw950.h3
IBM Power System L1022 (9786-22H) Firmware: from fw1060.00 before fw1060.81 — fixed in fw1060.81
IBM Power System L1024 (9786-42H) Firmware: from fw1060.00 before fw1060.81 — fixed in fw1060.81
IBM Power System L1122 (9856-22H) Firmware: from fw1110.00 before fw1110.31; fw1120.00 — fixed in fw1110.31
IBM Power System L1124 (9856-42H) Firmware: from fw1110.00 before fw1110.31; fw1120.00 — fixed in fw1110.31
IBM Power System S1012 (9028-21B) Firmware: from fw1060.00 before fw1060.81 — fixed in fw1060.81
IBM Power System S1014 (9105-41B) Firmware: from fw1060.00 before fw1060.81 — fixed in fw1060.81
IBM Power System S1022 (9105-22A) Firmware: from fw1060.00 before fw1060.81 — fixed in fw1060.81
IBM Power System S1022S (9105-22B) Firmware: from fw1060.00 before fw1060.81 — fixed in fw1060.81
IBM Power System S1024 (9105-42A) Firmware: from fw1060.00 before fw1060.81 — fixed in fw1060.81
IBM Power System S1112 (9242-21B) Firmware: fw1120.00
IBM Power System S1112 (9242-21T) Firmware: fw1120.00
IBM Power System S1114 (9824-41B) Firmware: from fw1110.00 before fw1110.31; fw1120.00 — fixed in fw1110.31
IBM Power System S1122 (9824-22A) Firmware: from fw1110.00 before fw1110.31; fw1120.00 — fixed in fw1110.31
IBM Power System S1122S (9824-22B) Firmware: from fw1110.00 before fw1110.31; fw1120.00 — fixed in fw1110.31
IBM Power System S1124 (9824-42A) Firmware: from fw1110.00 before fw1110.31; fw1120.00 — fixed in fw1110.31
IBM Power System S914 (9009-41G) Firmware: from fw950.00 before fw950.h3 — fixed in fw950.h3
IBM Power System S922 (9009-22G) Firmware: from fw950.00 before fw950.h3 — fixed in fw950.h3
IBM Power System S924 (9009-42G) Firmware: from fw950.00 before fw950.h3 — fixed in fw950.h3

How to fix

Upgrade to a fixed version: IBM Power System E1050 (9043-Mrx) Firmware fw1060.81; IBM Power System E1080 (9080-Hex) Firmware fw1060.81; IBM Power System E1150 (9043-Mru) Firmware fw1110.31; IBM Power System E1180 (9080-Heu) Firmware fw1110.31; IBM Power System E950 (9040-Mr9) Firmware fw950.h3; IBM Power System E980 (9080-M9S) Firmware fw950.h3; IBM Power System H922 (9223-22S) Firmware fw950.h3; IBM Power System H924 (9223-42S) Firmware fw950.h3; IBM Power System L1022 (9786-22H) Firmware fw1060.81; IBM Power System L1024 (9786-42H) Firmware fw1060.81; IBM Power System L1122 (9856-22H) Firmware fw1110.31; IBM Power System L1124 (9856-42H) Firmware fw1110.31. Check the vendor advisory for mitigations.

References

https://www.ibm.com/support/pages/node/7283232

Get alerted when CVE-2026-18821 or the next vulnerability affects your stack