CVE-2026-64172
Received Received - Intake

KVM AVIC IPI Virtualization Bypass on Hygon Family 18h CPUs

Publication date: 2026-07-19

Last updated on: 2026-07-19

Assigner: kernel.org

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.

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Meta Information

Published
2026-07-19
Last Modified
2026-07-19
Generated
2026-07-20
AI Q&A
2026-07-19
EPSS Evaluated
N/A
NVD
CVE-2026-64172
EUVD
EUVD-2026-45857

Affected Vendors & Products

Showing 3 associated CPEs
Vendor Product Version / Range
amd linux_kernel From 17h (inc)
amd family_17h *
hygon family_18h *

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Exploitability

CWE
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KEV
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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This vulnerability affects the Linux kernel's KVM (Kernel-based Virtual Machine) subsystem on Hygon Family 18h CPUs. It involves a hardware issue where stale data may cause the CPU to fail generating a required VM-Exit during IPI (Inter-Processor Interrupt) emulation. This leads to hung virtual CPUs and delays in guest execution.

Detection Guidance

Detection requires checking if the Linux kernel is running on Hygon Family 18h CPUs and if the KVM AVIC IPI virtualization is enabled. Use commands like 'lscpu' to verify CPU family and 'dmesg | grep -i kvm' to check KVM status. No direct commands detect this specific erratum.

Impact Analysis

If you use virtual machines on a system with Hygon Family 18h CPUs, this vulnerability could cause virtual CPUs to hang or become unresponsive. This may result in guest operating systems freezing or experiencing significant delays, potentially disrupting services running in those virtual machines.

Compliance Impact

This vulnerability primarily affects virtual machine performance and stability in Linux kernels running on Hygon Family 18h CPUs. It does not directly impact compliance with standards like GDPR or HIPAA, as those focus on data protection and privacy rather than system performance or availability.

Mitigation Strategies

Apply the latest Linux kernel update that includes the fix for this erratum. If immediate patching is not possible, disable KVM AVIC IPI virtualization manually by modifying kernel parameters or disabling KVM IPI virtualization features.

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