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Full vulnerability report · 2026
CVE-2026-85921High confidence

Windows Secure Kernel Mode Elevation of Privilege Vulnerability

Microsoft · Windows 11 version 26H1

8.2HighCVSS 3.1
Recommended action
Within 7 days

High technical severity; prioritise exposed affected systems while verifying vendor guidance.

Patch available
R
Operational reassessment

Published severity in operational context

Open reassessment dashboard →
Published severityHighOperational priority:Medium, lowered one band.downgradedsince 7 Oct 2026

Evidence used

  • No CISA KEV confirmation is currently recorded.
  • Exploitation requires an existing local or physical foothold with privileges.
  • EPSS is 0.35% for the current model date.

Compensating controls

  • Validate the affected product branch and deploy the verified fixed release.
  • Restrict local access and enforce least privilege on affected hosts.
  • Monitor vendor guidance and exploitation sources for a material change.

Verification

  1. Confirm that the asset runs Microsoft Windows 11 version 26H1 and falls inside the recorded affected range.
  2. Verify the installed build against the product-specific fixed version after deployment.
  3. Validate exposure, authentication requirements and compensating controls in the actual environment.
  4. Reopen this reassessment when CVSS, KEV, EPSS, exploit evidence or remediation changes.
Mitigation target: As exposure requiresRemediation target: Within 365 days

This automated reassessment organises public evidence. It does not know asset exposure, business impact or control effectiveness and does not replace CVSS or a human risk decision.

Direct vendor intelligence

Authoritative vendor CSAF and VEX advisories

Structured product status and remediation from the issuing vendor. Product-state explanations are always visible; large lists can be searched or downloaded.

1 current
msrc_CVE-2026-85921 · CSAF 2.0 · revision 3 · finalMicrosoft Security Response CenterWindows Secure Kernel Mode Elevation of Privilege Vulnerability
2 known affected

The vendor explicitly identifies these products as affected by this CVE.

  • Windows 11 Version 26H1 for ARM64-based Systems <10.0.28000.2956
  • Windows 11 version 26H1 for x64-based Systems <10.0.28000.2956
Summary
Microsoft
Remediation
10.0.28000.2956:Security Update:https://support.microsoft.com/help/5129194
Optional official sources

National CERT insights
?CERT means Computer Emergency Response Team; CSIRT is the closely related term Computer Security Incident Response Team.

Choose official national sources for this report. Each advisory shows its original language. Your selection is remembered on this device and included in shared links.

Official European source

ENISA European Vulnerability Database

Official EUVD identifiers, advisory evidence and known-exploited context. Missing fields are not treated as evidence of low risk.

1 current
ENISA EUVD identifier

EUVD-2026-77686

No EUVD known-exploited evidence

Double free in Windows Secure Kernel Mode allows an authorized attacker to elevate privileges locally.

EUVD state
Present in the current official mapping
Known exploitation
Not present in the current ENISA EUVD known-exploited dataset. This is not proof of no exploitation.
ENISA score
8.2 · CVSS 3.1
Advisory evidence
No linked advisory details stored yet
Recommended actionWithin 7 days

High technical severity; prioritise exposed affected systems while verifying vendor guidance.

Patch available
01

What, why and how

Double free in Windows Secure Kernel Mode allows an authorized attacker to elevate privileges locally.

What

Double free in Windows Secure Kernel Mode allows an authorized attacker to elevate privileges locally.

Why

The product calls free() twice on the same memory address.

How

An attacker operating through local access may attempt exploitation with elevated privileges. If successful, the issue may gain additional privileges.

What

Double free in Windows Secure Kernel Mode allows an authorized attacker to elevate privileges locally.

Why

The product calls free() twice on the same memory address.

How

An attacker operating through local access may attempt exploitation with elevated privileges. If successful, the issue may gain additional privileges.

02

Exploit reality and attack path

CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.

Observed exploitation
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
No confirmed evidence

No CISA KEV match was present at the last successful refresh. This means no confirmation from that source, not proof of no exploitation.

Public PoC / exploit material
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
None recorded

No exploit-tagged reference or CISA SSVC proof-of-concept state is currently recorded. Research may still exist outside the structured feeds.

Likely attack path
local access → Double Free → gain additional privileges
Attack surface
Local
Privileges required
High: elevated access is required
User interaction
None
Attack complexity
Low: no specialised conditions are recorded
Security boundary
Changed: exploitation can affect a different security authority
Weakness
?CWE means Common Weakness Enumeration: a standard category for the underlying weakness.
CWE-415 ↗

CWE-415: Double Free. The product calls free() twice on the same memory address.

CVSS vector
?CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity.
CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H/E:U/RL:O/RC:C

Common Vulnerability Scoring System 3.1: the compact vector below is decoded into plain language.

AVLocalAttack vector: The attacker needs local access to the vulnerable system.ACLowAttack complexity: No specialised conditions are required beyond attacker-controlled input.PRHighPrivileges required: The attacker needs elevated or administrative privileges.UINoneUser interaction: No action by another user is required.SChangedScope: The attack can affect a component governed by a different security authority.CHighConfidentiality impact: A successful attack can cause a major loss.IHighIntegrity impact: A successful attack can cause a major loss.AHighAvailability impact: A successful attack can cause a major loss.
Post-exploitation / living off the land
The issue can support a local privilege or sandbox boundary transition; normal system utilities may then be available in the gained context.
Privilege escalationCWE-415
A

Official authority intelligence

Only matched European and national findings are included. Language selectors and unavailable sources are omitted.

ENISA EUVD · EUVD-2026-77686Official EUVD mapping

Double free in Windows Secure Kernel Mode allows an authorized attacker to elevate privileges locally.

Official EUVD record ↗
BSI · German · WID-SEC-2026-3348Microsoft Windows 11 (Secure Kernel Mode): Schwachstelle ermöglicht Privilegieneskalation

Ein lokaler Angreifer kann eine Schwachstelle in Microsoft Windows 11 (Secure Kernel Mode) ausnutzen, um seine Privilegien zu erhöhen.

Official advisory ↗
CERT-FR · French · CERTFR-2026-AVI-1174Vulnérabilité dans Microsoft Windows

Une vulnérabilité a été découverte dans Microsoft Windows. Elle permet à un attaquant de provoquer une élévation de privilèges.

Official advisory ↗
JVN iPedia · Japanese · JVNDB-2026-036014マイクロソフトのMicrosoft Windows 11 26h1における二重解放に関する脆弱性

Windowsセキュアカーネルモードにおけるダブルフリーの脆弱性により、認可された攻撃者がローカルで権限を昇格させることが可能となります。

Official advisory ↗
03

Patch and workaround

Operational remediation based on structured source evidence.

Status
?Patch availability is based on structured fixed-version fields and authoritative update references. If no fix is verified, check the vendor advisory before making a change.
Patch available
Affected
Fixed
Action
10.0.28000.2956:Security Update:https://support.microsoft.com/help/5129194
Workaround
No verified workaround is recorded. Limit untrusted access and use least privilege until authoritative guidance is available.
04

Evidence and provenance

Published 14 Sept 2026 · Last source change 7 Oct 2026, 15:00 UTC · CWE-415 · Double Free

CVE recordCVE.org · 5.2
CVSS sourceCNA
EPSS source
?The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.
FIRST · tracked since 2026-09-15
European sourceENISA EUVD · EUVD-2026-77686
Product sourceVendor CSAF · Microsoft Security Response Center
Remediation sourceVendor CSAF · Microsoft Security Response Center
CWE sourceOther authority
NVD statusNVD enriched

Core structured fields are present and their contributing authorities are shown above.

Material change intelligence

What changed after publication

View recent updates ↗
  1. Affected versionsThe structured affected or fixed version information changed.
    Before
    Windows 11 version 26H1: 10.0.28000.0 < 10.0.28000.2956 · Fixed: 10.0.28000.2956:Security Update:https://support.microsoft.com/help/5129194
    After
    Windows 11 version 26H1: 10.0.28000.0 < 10.0.28000.2956 · Fixed: An authoritative update reference is available, but the fixed version is not recorded in the structured CVE fields. Check the linked vendor advisory for the applicable release.
    CNA ↗
  2. Affected versionsThe structured affected or fixed version information changed.
    Before
    Windows 11 version 26H1: 10.0.28000.0 < 10.0.28000.2956 · Fixed: 10.0.28000.2956:Security Update:https://support.microsoft.com/help/5129194
    After
    Windows 11 version 26H1: 10.0.28000.0 < 10.0.28000.2956 · Fixed: An authoritative update reference is available, but the fixed version is not recorded in the structured CVE fields. Check the linked vendor advisory for the applicable release.
    CNA ↗
  3. Affected versionsThe structured affected or fixed version information changed.
    Before
    Windows 11 version 26H1: 10.0.28000.0 < 10.0.28000.2956 · Fixed: 10.0.28000.2956:Security Update:https://support.microsoft.com/help/5129194
    After
    Windows 11 version 26H1: 10.0.28000.0 < 10.0.28000.2956 · Fixed: An authoritative update reference is available, but the fixed version is not recorded in the structured CVE fields. Check the linked vendor advisory for the applicable release.
    CNA ↗
  4. Affected versionsThe structured affected or fixed version information changed.
    Before
    Windows 11 version 26H1: 10.0.28000.0 < 10.0.28000.2956 · Fixed: 10.0.28000.2956:Security Update:https://support.microsoft.com/help/5129194
    After
    Windows 11 version 26H1: 10.0.28000.0 < 10.0.28000.2956 · Fixed: An authoritative update reference is available, but the fixed version is not recorded in the structured CVE fields. Check the linked vendor advisory for the applicable release.
    CNA ↗
  5. Affected versionsThe structured affected or fixed version information changed.
    Before
    Windows 11 version 26H1: 10.0.28000.0 < 10.0.28000.2956 · Fixed: 10.0.28000.2956:Security Update:https://support.microsoft.com/help/5129194
    After
    Windows 11 version 26H1: 10.0.28000.0 < 10.0.28000.2956 · Fixed: An authoritative update reference is available, but the fixed version is not recorded in the structured CVE fields. Check the linked vendor advisory for the applicable release.
    CNA ↗
  6. Affected versionsThe structured affected or fixed version information changed.
    Before
    Windows 11 version 26H1: 10.0.28000.0 < 10.0.28000.2956 · Fixed: An authoritative update reference is available, but the fixed version is not recorded in the structured CVE fields. Check the linked vendor advisory for the applicable release.
    After
    Windows 11 version 26H1: 10.0.28000.0 < 10.0.28000.2956 · Fixed: 10.0.28000.2956:Security Update:https://support.microsoft.com/help/5129194
    Microsoft Security Response Center ↗
  7. Affected versionsThe structured affected or fixed version information changed.
    Before
    Windows 11 version 26H1: 10.0.28000.0 < 10.0.28000.2956 · Fixed: No fixed version is explicitly recorded in the structured CVE data.
    After
    Windows 11 version 26H1: 10.0.28000.0 < 10.0.28000.2956 · Fixed: 10.0.28000.2956:Security Update:https://support.microsoft.com/help/5129194
    Microsoft Security Response Center ↗
  8. Remediation statusRemediation status changed from Awaiting fix to Patch available.
    Before
    Awaiting fix
    After
    Patch available
    Microsoft Security Response Center ↗
  9. Affected versionsThe structured affected or fixed version information changed.
    Before
    Windows 11 version 26H1: 10.0.28000.0 < 10.0.28000.2956 · Fixed: 10.0.28000.2956:Security Update:https://support.microsoft.com/help/5129194
    After
    Windows 11 version 26H1: 10.0.28000.0 < 10.0.28000.2956 · Fixed: An authoritative update reference is available, but the fixed version is not recorded in the structured CVE fields. Check the linked vendor advisory for the applicable release.
    CNA ↗
  10. ENISA EUVD mappingEUVD-2026-77686 was added to the official ENISA EUVD mapping for this CVE.
    Before
    not recorded
    After
    {"euvdId":"EUVD-2026-77686"}
    ENISA EUVD ↗
  11. Catalogue recordCVE added to the BlackTree catalogue.
    CNA ↗
Material fields only · duplicate refreshes suppressed · history retained for the configured operational retention period
CVE published
Fixed release or patch reference recorded
Fixed release recorded from official guidance
ENISA EUVD · EUVD-2026-77686↗CVE authority or vendor reference↗Official CVE record (CNA and ADP data)↗NVD record↗
Technical terms and abbreviations used in this report
CVE
Common Vulnerabilities and Exposures: the public identifier for one disclosed vulnerability.
CVSS
Common Vulnerability Scoring System: a technical severity framework; it is not patching priority by itself.
EPSS
Exploit Prediction Scoring System: FIRST's estimate of the probability that exploitation activity will be observed in the next 30 days; it is a forecast, not confirmation.
CWE
Common Weakness Enumeration: the standard category describing the underlying software or hardware weakness.
CNA
CVE Numbering Authority: an organisation authorised to assign and publish CVE records.
CISA ADP
Cybersecurity and Infrastructure Security Agency Authorized Data Publisher: structured enrichment added to a CVE record.
NVD
National Vulnerability Database: NIST's enrichment service for CVE records.
CERT / CSIRT
A computer security incident response team that publishes warnings or coordinates incident response.
PoC
Proof of concept: public material that demonstrates or helps reproduce exploitation.
CSAF
Common Security Advisory Framework: a machine-readable format for security advisories.
LoTL
Living off the land: abuse of legitimate tools or system functions during an attack.
Free version - for non-commercial use only.CVE-2026-85921 · cve.blacktree.nl