In the Linux kernel, the following vulnerability has been resolved: KVM: SVM: Disable AVIC IPI virtualization on Hygon Family 18h (erratum #1235)… (CVE-2026-64172)
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.
AI Analysis
Technical Summary
The Linux kernel vulnerability CVE-2026-64172 concerns KVM's handling of AVIC IPI virtualization on Hygon Family 18h CPUs, which are derived from AMD Family 17h silicon and share erratum #1235. The hardware may read a stale IsRunning=1 bit during ICR write emulation, causing the absence of a VM-Exit that signals AVIC_IPI_FAILURE_TARGET_NOT_RUNNING on the sending vCPU. Without this VM-Exit, KVM fails to wake blocking target vCPUs, resulting in hung vCPUs and unbounded guest execution delays. The mitigation extends the existing AMD Family 17h workaround by disabling AVIC IPI virtualization on Hygon Family 18h CPUs, preventing KVM from setting IsRunning=1 and ensuring every non-self IPI generates a VM-Exit for proper emulation.
Potential Impact
The vulnerability causes KVM to miss VM-Exits required to wake blocking virtual CPUs, leading to hung vCPUs and potentially unbounded delays in guest virtual machine execution. This impacts the stability and responsiveness of virtualized environments running on affected Hygon Family 18h CPUs.
Mitigation Recommendations
A fix has been implemented by extending the existing AMD Family 17h erratum #1235 workaround to Hygon Family 18h CPUs. This disables AVIC IPI virtualization, ensuring correct VM-Exit generation and emulation. Users should apply the updated Linux kernel version containing this fix. Patch status is confirmed as resolved in the Linux kernel; no additional mitigation is required beyond applying the official fix.
In the Linux kernel, the following vulnerability has been resolved: KVM: SVM: Disable AVIC IPI virtualization on Hygon Family 18h (erratum #1235)… (CVE-2026-64172)
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.
CVSS v3.1
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The Linux kernel vulnerability CVE-2026-64172 concerns KVM's handling of AVIC IPI virtualization on Hygon Family 18h CPUs, which are derived from AMD Family 17h silicon and share erratum #1235. The hardware may read a stale IsRunning=1 bit during ICR write emulation, causing the absence of a VM-Exit that signals AVIC_IPI_FAILURE_TARGET_NOT_RUNNING on the sending vCPU. Without this VM-Exit, KVM fails to wake blocking target vCPUs, resulting in hung vCPUs and unbounded guest execution delays. The mitigation extends the existing AMD Family 17h workaround by disabling AVIC IPI virtualization on Hygon Family 18h CPUs, preventing KVM from setting IsRunning=1 and ensuring every non-self IPI generates a VM-Exit for proper emulation.
Potential Impact
The vulnerability causes KVM to miss VM-Exits required to wake blocking virtual CPUs, leading to hung vCPUs and potentially unbounded delays in guest virtual machine execution. This impacts the stability and responsiveness of virtualized environments running on affected Hygon Family 18h CPUs.
Mitigation Recommendations
A fix has been implemented by extending the existing AMD Family 17h erratum #1235 workaround to Hygon Family 18h CPUs. This disables AVIC IPI virtualization, ensuring correct VM-Exit generation and emulation. Users should apply the updated Linux kernel version containing this fix. Patch status is confirmed as resolved in the Linux kernel; no additional mitigation is required beyond applying the official fix.
Technical Details
- Gcve Source
- db.gcve.eu
- Osv Id
- GHSA-4cvr-85r6-xwmj
- Osv Schema Version
- 1.4.0
- Aliases
- ["CVE-2026-64172"]
- Ecosystems
- []
- Database Specific Severity
- null
- Cvss Version
- null
Threat ID: 6a5d27a82a4a8d598912a88b
Added to database: 07/19/2026, 19:38:16 UTC
Last enriched: 07/19/2026, 19:42:46 UTC
Last updated: 07/20/2026, 19:41:21 UTC
Views: 14
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