CVE-2026-64513

/// Technical description

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

KVM: x86: Unconditionally recompute CR8 intercept on PPR update

The TPR_THRESHOLD field in the VMCS is used by VMX to induce VM exits

when the guest's virtual TPR falls under the specified threshold,

allowing KVM to inject previously masked interrupts.

KVM handles these VM exits in handle_tpr_below_threshold().

Commit eb90f3417a0c ("KVM: vmx: speed up TPR below threshold vmexits")

optimized this function by calling apic_update_ppr() instead of raising

KVM_REQ_EVENT. apic_update_ppr() then raises KVM_REQ_EVENT if there is

a pending, deliverable interrupt.

However, if there are no new interrupts pending, apic_update_ppr() does

not issue the request. Thus, kvm_lapic_update_cr8_intercept() and

vmx_update_cr8_intercept() are not called before VM entry, which results

in a high, stale TPR_THRESHOLD. This is problematic due to the following

sentence in 28.2.1.1 "VM-Execution Control Fields" in the SDM:

The following che

/// 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