CVE-2026-74516

A flaw was found in KVM (Kernel-based Virtual Machine). When the Advanced Virtual Interrupt Controller (AVIC) is inhibited while a nested guest (L2) is active, KVM fails to properly update x2APIC MSR intercepts for the primary guest (L1). This allows the L1 guest to read the host's APIC state, send arbitrary interrupts, and change task priority, ultimately leading to a Denial of Service (DoS) of the host system.

This vulnerability is rated as Important because an unprivileged guest running on an AMD-based KVM host can break guest-to-host isolation to disrupt host stability or trigger a denial of service, presenting high host-level impact despite requiring specific virtualization configurations. The issue is restricted to environments utilizing AMD hardware with interrupt acceleration where nested hypervisors are actively deployed. Deployments that do not delegate virtualization capabilities to guest workloads or disable nested virtualization are not exposed.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.