CVE-2026-43483
MediumCVSS 5.5Exploitation Probability (EPSS)
Low risk2th percentile - higher than 2% of all known CVEs
Summary
In the Linux kernel, a vulnerability was found in the KVM module for AMD processors (SVM). The issue is that CR8 write interception is not properly cleared when AVIC (Advanced Virtual Interrupt Controller) is activated, leaving it enabled permanently. Combined with another TPR sync bug, this causes the TPR value seen by hardware to become out of sync, which is fatal for Windows virtual machines.
Risk Assessment
For organizations, the risk involves potential crashes of Windows virtual machines on AMD hosts, leading to service disruptions and data loss. The vulnerability can be exploited to destabilize the virtualization environment.
Recommendation
It is recommended to immediately update the Linux kernel to a version containing the fix (commit d02e48830e3f and related changes). Also monitor whether AVIC is active and if unexpected CR8 interceptions occur.
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Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: KVM: SVM: Set/clear CR8 write interception when AVIC is (de)activated Explicitly set/clear CR8 write interception when AVIC is (de)activated to fix a bug where KVM leaves the interception enabled after AVIC is activated. E.g. if KVM emulates INIT=>WFS while AVIC is deactivated, CR8 will remain intercepted in perpetuity. On its own, the dangling CR8 intercept is "just" a performance issue, but combined with the TPR sync bug fixed by commit d02e48830e3f ("KVM: SVM: Sync TPR from LAPIC into VMCB::V_TPR even if AVIC is active"), the danging intercept is fatal to Windows guests as the TPR seen by hardware gets wildly out of sync with reality. Note, VMX isn't affected by the bug as TPR_THRESHOLD is explicitly ignored when Virtual Interrupt Delivery is enabled, i.e. when APICv is active in KVM's world. I.e. there's no need to trigger update_cr8_intercept(), this is firmly an SVM implementation flaw/detail. WARN if KVM gets a CR8 write #VMEXIT while AVIC is active, as KVM should never enter the guest with AVIC enabled and CR8 writes intercepted. [Squash fix to avic_deactivate_vmcb. - Paolo]
Vulnerability data from NVD (NIST) · CISA KEV · EPSS

