CVE-2026-98720Hinoki check available

Host-register access via stale nested-VM MSR bitmap

Published Oct 18, 2026 · Updated Oct 18, 2026

Isolation bypass in Linux KVM allows guest OS users to read and write the host task-priority register through nested VM execution. In arch/x86/kvm/vmx/nested.c, copy_enlightened_to_vmcs12 fails to invalidate the MSR bitmap when runtime eVMCS controls change. Exposure requires nested VMX with eVMCS, an L1 guest that does not intercept TPR writes, and an L2 guest run with TPR virtualization enabled and then disabled; the documented consequence is access to L0's TPR, not arbitrary host memory or code execution.

CVSS severityUnavailable
Unscored
EPSS probability0.17%
Next 30 days · Oct 19, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkAvailable
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Summary

What happened

Isolation bypass in Linux KVM allows guest OS users to read and write the host task-priority register through nested VM execution. In arch/x86/kvm/vmx/nested.c, copy_enlightened_to_vmcs12 fails to invalidate the MSR bitmap when runtime eVMCS controls change. Exposure requires nested VMX with eVMCS, an L1 guest that does not intercept TPR writes, and an L2 guest run with TPR virtualization enabled and then disabled; the documented consequence is access to L0's TPR, not arbitrary host memory or code execution.

The record

CVE
CVE-2026-98720
Published
Oct 18, 2026
Updated
Oct 18, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1611
Attack vector
local
Privileges
Unavailable

Timeline

How it unfolded

  1. Oct 18, 2026CVE publishedPublication date reported by the CVE source.
  2. Oct 18, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

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  1. Affected versionversion=502d2bf5f2fd7c05adc2d4f057910bd5d4c4c63e <1e497e3bdab6983deb68a1d26b488027deb4527f
  2. Affected versionversion=502d2bf5f2fd7c05adc2d4f057910bd5d4c4c63e <2abb25273c82061dd4670690c81c319c03740bf6
  3. Affected versionversion=502d2bf5f2fd7c05adc2d4f057910bd5d4c4c63e <2db11598b59f16ddb6420693f9a4ac4efc3d4789
  4. Affected versionversion=502d2bf5f2fd7c05adc2d4f057910bd5d4c4c63e <f6189e26d0237e47e2f04f9cb1e43fd19a9b2f3a
  5. Affected versionversion=5.17

What conditions does exploitation require?

Attack vectorlocal
Required privilegesUnavailable in this record.

What is affected?

The Linux Kernel Organization · Linuxversion=502d2bf5f2fd7c05adc2d4f057910bd5d4c4c63e <1e497e3bdab6983deb68a1d26b488027deb4527f; version=502d2bf5f2fd7c05adc2d4f057910bd5d4c4c63e <2abb25273c82061dd4670690c81c319c03740bf6; version=502d2bf5f2fd7c05adc2d4f057910bd5d4c4c63e <2db11598b59f16ddb6420693f9a4ac4efc3d4789; version=502d2bf5f2fd7c05adc2d4f057910bd5d4c4c63e <f6189e26d0237e47e2f04f9cb1e43fd19a9b2f3a; version=5.17

Published CVSS scores

No CVSS assessment is available in this record.

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

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Activity data is delayed. The latest report is Sep 28, 2026.

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No observations available

Sep 22, 2026Sep 28, 2026
Latest reporting daySep 28, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
PrivilegesUnavailable
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1611Escape to Host

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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