CVE-2026-74516

/// Technical description

In the Linux kernel, the following vulnerability has been resolved:

KVM: SVM: Update x2APIC MSR intercepts if AVIC is inhibited while L2 is active

Always update x2APIC MSR intercepts for L1 when AVIC is deactivated, even

if L2 is active and KVM is using a separate MSR bitmap to run L2. If AVIC

is fully enabled prior to running L2, and is then inhibited while L2 is

active (for a VM-scoped inhibit), then KVM will run L1 with AVIC disabled,

but with x2APIC MSR intercepts disabled, i.e. will allow L1 to read most of

the host's APIC state, send arbitrary interrupts, change task priority, and

ultimately trivially DoS the host.

E.g. sending a self-IPI in L1 on HYPERV_REENLIGHTENMENT_VECTOR, 0xee, with

CONFIG_HYPERV=n in the host kernel as a "safe" PoC, yields:

Spurious interrupt (vector 0xee) on CPU#425. Acked

And hacking KVM to abuse kvm_set_posted_intr_wakeup_handler() to register a

handler and WARN on POSTED_INTR_WAKEUP_VECTOR yields:

------------[ cut here ]------------

WARNI

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References