Vulnerability · Published Aug 19, 2026 · Assigned by ibm

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

High 7.5

In plain English

A high-severity out-of-bounds write in PowerVM Hypervisor from IBM. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 21% of all known vulnerabilities).

Severity (CVSS 3.1)7.5High

Exploit odds (30 days)0.3%top 78.8% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official 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 (as reported)

Vendor	Product	Versions
IBM	PowerVM Hypervisor	FW1120.00FW1110.00 – through FW1110.30FW1060.00 – through FW1060.80FW950.00 – through FW950.H2

Weakness: CWE-787 · Vector: CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

References

https://www.ibm.com/support/pages/node/7283232 vendor-advisory, patch