In the Linux kernel, the following vulnerability has been resolved: KVM: x86: Unconditionally recompute CR8 intercept…
Source GCVE Database
Not known to be exploited.
Data as of 10/24/2026, 22:16:04 UTC
No CVSS score from NVD or the CNA
- Exploitation
Not in CISA KEV, no exploitation reported
- EPSS
- 0.2% chance of exploitation in 30 days – higher than 12% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
What to do
AI-suggested
The description indicates that a code fix has been implemented in the Linux kernel to address this issue by ensuring CR8 intercepts are updated correctly on all PPR update paths. Users should monitor official Linux kernel advisories and update to fixed kernel versions once available. No alternative mitigations are specified.
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 check is performed if the “use TPR shadow” VM-execution control is 1 and the “virtualize APIC accesses” and “virtual-interrupt delivery” VM-execution controls are both 0: the value of bits 3:0 of the TPR threshold VM-execution control field should not be greater than the value of bits 7:4 of VTPR. This error condition is typically not observed when KVM runs on a bare metal system because modern processors support APICv, which enables virtual-interrupt delivery, and which KVM uses when possible. This causes the processor to no longer generate TPR-below-threshold exits and to no longer check TPR_THRESHOLD on entry. However, when running on older platforms, or under nested virtualization on a hypervisor that does not support virtual-interrupt delivery and enforces this check (like Hyper-V) this can cause a VM entry failure with hardware error 0x7, as seen in [1]. Call kvm_lapic_update_cr8_intercept() if apic_update_ppr() does not find a deliverable interrupt (and thus does not raise KVM_REQ_EVENT). Remove calls to kvm_lapic_update_cr8_intercept() on paths that end up in apic_update_ppr(), as they now become redundant. This ensures that any path that updates the guest's PPR also figures out if KVM needs to wait for a TPR change (using TPR_THRESHOLD on VMX or CR8 intercepts on SVM).
Impact
This vulnerability can cause virtual machine entry failures with hardware error 0x7 on affected systems, particularly older hardware without APICv support or nested virtualization environments on hypervisors that enforce strict VMX execution control checks. This may lead to denial of service for virtual machines relying on KVM on such platforms. There is no indication of code execution or privilege escalation from the provided data.
References
- nvd.nist.gov/vuln/detail/CVE-2026-64513 (opens in a new tab)
- git.kernel.org/stable/c/8c8e8ac22ee17d52f9eb2bc814bca7fab90fb8df (opens in a new tab)
- git.kernel.org/stable/c/bb365a506b1e6fb050c0fceaad354fe395385ef0 (opens in a new tab)
- git.kernel.org/stable/c/ff9c4c6428883182960cfe5c78928f0896d80ebc (opens in a new tab)