CVE-2026-64172 KVM: SVM: Disable AVIC IPI virtualization on Hygon Family 18h (erratum #1235)
A hardware erratum in Hygon CPUs causes KVM to miss vCPU wakeups, leading to guest hangs and denial of service.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-64172?
CVE-2026-64172 is a high-severity denial of service vulnerability in Linux kernel, published on 19 Jul 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: Disable AVIC IPI virtualization on Hygon Family 18h (erratum #1235)
Hygon Family 18h CPUs are derived from AMD Family 17h (Zen1) silicon and share the same erratum #1235: hardware may read a stale IsRunning=1 bit during ICR write emulation and silently fail to generate an AVIC_IPI_FAILURE_TARGET_NOT_RUNNING VM-Exit on the sending vCPU.
The absence of the VM-Exit causes KVM to miss the required wakeup of blocking target vCPUs, leading to hung vCPUs and unbounded delays in guest execution.
Extend the existing AMD Family 17h erratum #1235 workaround to also cover Hygon Family 18h. With IPI virtualization disabled, KVM never sets IsRunning=1 in the Physical ID table, so every non-self IPI generates a VM-Exit and is correctly emulated.
Which versions are affected by CVE-2026-64172?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-64172?
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-2026-64172 being exploited?
There is no known exploitation of CVE-2026-64172 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2026-64172, DEBIAN-CVE-2026-64172, GHSA-4cvr-85r6-xwmj, UBUNTU-CVE-2026-64172.