CVE-2026-98164

Host-kernel BUG via cross-address-space write-tracking miss

Published Sep 29, 2026 · Updated Sep 29, 2026

A write-tracking flaw in Linux KVM's x86 MMU allows attackers controlling a guest to trigger a host-kernel BUG through SMM address spaces. The kvm_gfn_is_write_tracked() function checks only the supplied memory slot even though shadow pages are shared across address spaces, allowing mmu_try_to_unsync_pages() to mark an upper-level shadow page unsynchronized. The documented failure involved SMM and nested VMX; synchronization then reached a BUG in pte_list_remove(), with no documented code-execution impact.

CVSS severityUnavailable
Unscored
EPSS probability0.15%
Next 30 days · Oct 19, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

A write-tracking flaw in Linux KVM's x86 MMU allows attackers controlling a guest to trigger a host-kernel BUG through SMM address spaces. The kvm_gfn_is_write_tracked() function checks only the supplied memory slot even though shadow pages are shared across address spaces, allowing mmu_try_to_unsync_pages() to mark an upper-level shadow page unsynchronized. The documented failure involved SMM and nested VMX; synchronization then reached a BUG in pte_list_remove(), with no documented code-execution impact.

The record

CVE
CVE-2026-98164
Published
Sep 29, 2026
Updated
Sep 29, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1499
Attack vector
local
Privileges
Unavailable

Timeline

How it unfolded

  1. Sep 29, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 29, 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?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=4.2
  2. Affected versionversion=699023e239658e62da6f42f47d31b54788521ec1 <09aa68552d2542cc6c23edd1568ac265dc5d886f
  3. Affected versionversion=699023e239658e62da6f42f47d31b54788521ec1 <0f38453cdb2e17566ccb7c0f3dabd5bd21caca26
  4. Affected versionversion=699023e239658e62da6f42f47d31b54788521ec1 <429b6f43b4d8c98988fdca99e02dc156134e3d77
  5. Affected versionversion=699023e239658e62da6f42f47d31b54788521ec1 <c0a9bd5fca0b5f2dea32b0fc31350e71e8648112
  6. Affected versionversion=699023e239658e62da6f42f47d31b54788521ec1 <d8636c8f9f95d0fd1e2f6f1cad0d5757aa6f212a
  7. Affected versionversion=699023e239658e62da6f42f47d31b54788521ec1 <ec8fcaf354c1cbb36755d48e9f5a00c9591349e5

What conditions does exploitation require?

Attack vectorlocal
Required privilegesUnavailable in this record.

What is affected?

The Linux Kernel Organization · Linuxversion=4.2; version=699023e239658e62da6f42f47d31b54788521ec1 <09aa68552d2542cc6c23edd1568ac265dc5d886f; version=699023e239658e62da6f42f47d31b54788521ec1 <0f38453cdb2e17566ccb7c0f3dabd5bd21caca26; version=699023e239658e62da6f42f47d31b54788521ec1 <429b6f43b4d8c98988fdca99e02dc156134e3d77; version=699023e239658e62da6f42f47d31b54788521ec1 <c0a9bd5fca0b5f2dea32b0fc31350e71e8648112; version=699023e239658e62da6f42f47d31b54788521ec1 <d8636c8f9f95d0fd1e2f6f1cad0d5757aa6f212a; version=699023e239658e62da6f42f47d31b54788521ec1 <ec8fcaf354c1cbb36755d48e9f5a00c9591349e5

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

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

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

T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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