CVE-2026-64172: KVM: SVM: Disable AVIC IPI virtualization on Hygon Family 18h (erratum #1235)
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 AVICIPIFAILURETARGETNOTRUNNING 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.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Patch erratum #1235 - Configuration
Extend the existing AMD Family 17h erratum #1235 workaround to Hygon Family 18h CPUs by disabling AVIC IPI virtualization (KVM: SVM: Disable AVIC IPI virtualization on Hygon Family 18h, erratum #1235) so KVM avoids relying on stale IsRunning=1 and prevents hung vCPUs/unbounded delays during ICR write emulation.
Linux kernel KVM (SVM) AVIC IPI virtualization = disabled
Event History
Frequently Asked Questions
What is the severity of CVE-2026-64172?
The severity of CVE-2026-64172 is rated at 37.
How do I fix CVE-2026-64172?
To remediate CVE-2026-64172, disable AVIC IPI virtualization on Hygon Family 18h CPUs.
Which systems are affected by CVE-2026-64172?
CVE-2026-64172 affects systems using Hygon Family 18h CPUs derived from AMD Family 17h (Zen1) and the Red Hat Linux kernel.
What does CVE-2026-64172 address?
CVE-2026-64172 addresses an issue where hardware may read a stale IsRunning=1 bit during interrupt processing.
When was CVE-2026-64172 published?
CVE-2026-64172 was published on July 19, 2026.