CVE-2026-43483 KVM: SVM: Set/clear CR8 write interception when AVIC is (de)activated
A flaw in Linux KVM SVM implementation causes Windows guests to crash due to TPR synchronization issues when AVIC is activated.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-43483?
CVE-2026-43483 is a medium-severity denial of service vulnerability in Linux kernel, published on 13 May 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
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]
Which versions are affected by CVE-2026-43483?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-43483?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-43483 being exploited?
There is no known exploitation of CVE-2026-43483 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2026-43483, DEBIAN-CVE-2026-43483, GHSA-8rg3-3364-c6fh, ROOT-OS-DEBIAN-11-CVE-2026-43483, ROOT-OS-UBUNTU-2204-CVE-2026-43483, ROOT-OS-UBUNTU-2404-CVE-2026-43483 and 1 more.