CVE-2026-99082

Write-tracking bypass via stale SMM MMIO entries

Published Oct 23, 2026 · Updated Oct 23, 2026

Write-tracking bypass in Linux x86 KVM allows guest OS users to write RAM without invalidating cached translations via stale MMIO entries. The vcpu_cache_mmio_info() and vcpu_match_mmio_gen() helpers use the normal address-space generation even in System Management Mode (SMM), leaving obsolete SMM entries valid. After an SMM memslot update and return to normal execution, a RAM write misclassified as MMIO bypasses write tracking; nested EPT backing pages retain stale shadow translations, without a demonstrated host escape.

CVSS severityUnavailable
Unscored
EPSS probability0.16%
Next 30 days · Nov 1, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Write-tracking bypass in Linux x86 KVM allows guest OS users to write RAM without invalidating cached translations via stale MMIO entries. The vcpu_cache_mmio_info() and vcpu_match_mmio_gen() helpers use the normal address-space generation even in System Management Mode (SMM), leaving obsolete SMM entries valid. After an SMM memslot update and return to normal execution, a RAM write misclassified as MMIO bypasses write tracking; nested EPT backing pages retain stale shadow translations, without a demonstrated host escape.

The record

CVE
CVE-2026-99082
Published
Oct 23, 2026
Updated
Oct 23, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
Unavailable
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Oct 23, 2026CVE publishedPublication date reported by the CVE source.
  2. Oct 23, 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 <2566780c684c9c21241d409d790087c73070f312
  3. Affected versionversion=699023e239658e62da6f42f47d31b54788521ec1 <7fd4e64f4bbc8c35ae8f0d2a1fb5b77a76d5b4fd
  4. Affected versionversion=699023e239658e62da6f42f47d31b54788521ec1 <a63f79d9da9468952396af73e1e53330845cf876
  5. Affected versionversion=699023e239658e62da6f42f47d31b54788521ec1 <b3e6212dea2e4328a841ceb37f377583176dc735
  6. Affected versionversion=699023e239658e62da6f42f47d31b54788521ec1 <e792a9ace39d2812a5b342a1987186c7bc653204

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=4.2; version=699023e239658e62da6f42f47d31b54788521ec1 <2566780c684c9c21241d409d790087c73070f312; version=699023e239658e62da6f42f47d31b54788521ec1 <7fd4e64f4bbc8c35ae8f0d2a1fb5b77a76d5b4fd; version=699023e239658e62da6f42f47d31b54788521ec1 <a63f79d9da9468952396af73e1e53330845cf876; version=699023e239658e62da6f42f47d31b54788521ec1 <b3e6212dea2e4328a841ceb37f377583176dc735; version=699023e239658e62da6f42f47d31b54788521ec1 <e792a9ace39d2812a5b342a1987186c7bc653204

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
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

No sourced classifications are available.

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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Your stack

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