CVE-2026-12855

Name of the Vulnerable Software and Affected Versions InsydeH2O Kernel versions 5.5 and earlier

Description An unvalidated memory boundary in the code developed for HP projects allows for arbitrary code execution. Specifically, an out-of-bounds write exists in the H19WMIHandlerSmm module (GUID f1946499-571b-44c3-9b9c-cc55210b0c02). An attacker with local kernel privileges can trigger a Software SMI (System Management Interrupt), which is a high-priority interrupt that suspends all other system activities to execute code in System Management Mode (SMM). This allows for a privilege escalation from ring 0 (kernel) to ring -2 (SMM), enabling arbitrary physical memory writes, including SMRAM. This can lead to the implantation of a persistent SMM rootkit that bypasses Secure Boot and survives operating system reinstallation.

Recommendations Apply the UEFI BIOS firmware update provided by HP for the specific affected model. Implement driver blocklisting and enable HVCI/Device Guard to prevent the initial kernel compromise required to trigger this issue.