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Full vulnerability report · 2021
CVE-2021-26863High confidence

Windows Win32k Elevation of Privilege Vulnerability

Microsoft · Windows 10 Version 1803

7.0HighCVSS 3.1
Recommended action
Within 7 days

High technical severity with public exploit material referenced by a structured source; prioritise exposed affected systems while verifying vendor guidance.

Patch available
R
Operational reassessment

Published severity in operational context

Open reassessment dashboard →
Published severityHighOperational priority:High, unchanged from published severity.unchanged

Evidence used

  • No CISA KEV confirmation is currently recorded.
  • A structured source references public exploit or proof-of-concept material.
  • Exploitation requires an existing local or physical foothold with privileges.
  • EPSS is 11.85% 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.
  • Increase monitoring for the attack path and post-exploitation behaviour described in the report.

Verification

  1. Confirm that the asset runs Microsoft Windows 10 Version 1803 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: Within 30 daysRemediation target: Within 180 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.

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-2021-13647

No EUVD known-exploited evidence

Windows Win32k Elevation of Privilege Vulnerability

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
7.0 · CVSS 3.1
Advisory evidence
No linked advisory details stored yet
Recommended actionWithin 7 days

High technical severity with public exploit material referenced by a structured source; prioritise exposed affected systems while verifying vendor guidance.

Patch available
01

What, why and how

Windows Win32k Elevation of Privilege Vulnerability

What

Windows Win32k Elevation of Privilege Vulnerability

Why

The product does not properly assign, modify, track, or check privileges for an actor, creating an unintended sphere of control for that actor.

How

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

What

Windows Win32k Elevation of Privilege Vulnerability

Why

The product does not properly assign, modify, track, or check privileges for an actor, creating an unintended sphere of control for that actor.

How

An attacker operating through local access may attempt exploitation with low 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.
Reference recorded

A structured CVE source labels at least one public reference as exploit material. BlackTree has not independently validated that it is safe, reliable or weaponised.

Likely attack path
local access → Improper Privilege Management → gain additional privileges
Attack surface
Local
Privileges required
Low: a basic authenticated account is required
User interaction
None
Attack complexity
High: exploitation depends on specific conditions
Security boundary
Unchanged: impact remains within the vulnerable component's security authority
Weakness
?CWE means Common Weakness Enumeration: a standard category for the underlying weakness.
CWE-269 ↗

CWE-269: Improper Privilege Management. The product does not properly assign, modify, track, or check privileges for an actor, creating an unintended sphere of control for that actor.

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:H/PR:L/UI:N/S:U/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.ACHighAttack complexity: Successful exploitation depends on specific conditions outside the attacker's direct control.PRLowPrivileges required: The attacker needs basic user-level privileges.UINoneUser interaction: No action by another user is required.SUnchangedScope: The security impact remains within the vulnerable component's 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-269Public exploit reference
A

Official authority intelligence

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

ENISA EUVD · EUVD-2021-13647Official EUVD mapping

Windows Win32k Elevation of Privilege Vulnerability

Official EUVD record ↗
Cyber Security Agency of Singapore · English · CSA-SB-20210317Security Bulletin 17 Mar 2021

The Cyber Security Agency of Singapore included this CVE in its official Security Bulletin 17 Mar 2021, published on 17 March 2021. Open the linked bulletin for the product, severity and reference information published in that issue.

Official advisory ↗
CERT-FR · French · CERTFR-2021-AVI-181Multiples vulnérabilités dans Microsoft Windows

fr-FR/security-guidance Référence CVE CVE-2021-1640 https://www.cve.org/CVERecord?id=CVE-2021-1640 Référence CVE CVE-2021-1729 https://www.cve.org/CVERecord?id=CVE-2021-1729 Référence CVE CVE-2021-24090 https://www.cve.org/CVERecord?id=CVE-2021-24090 Référence CVE CVE-2021-24095 https://www.cve.org/CVERecord?id=CVE-2021-24095 Référence CVE CVE-2021-24107 https://www.cve.org/CVERecord?id=CVE-2021-24107 Référence CVE CVE-2021-26860 https://www.cve.org/CVERecord?id=CVE-2021-26860 Référence CVE CVE-2021-26861 https://www.cve.org/CVERecord?id=CVE-2021-26861 Référence CVE CVE-2021-26862 https://www.cve.org/CVERecord?id=CVE-2021-26862 Référence CVE CVE-2021-26863 https://www.cve.org/CVERecord?id=CVE-2021-26863 Référence CVE CVE-2021-26864 https://www.cve.org/CVERecord?id=CVE-2021-26864 Référence CVE CVE-2021-26865 https://www.cve.org/CVERecord?id=CVE-2021-26865 Référence CVE CVE-2021-26866 https://www.cve.org/CVERecord?id=CVE-2021-26866 Référence CVE CVE-2021-26867 https://www.cve.org/CVERecord?id=CVE-2021-26867 Référence CVE CVE-2021-26868 https://www.cve.org/CVERecord?id=CVE-2021-26868 Référence CVE CVE-2021-26869 https://www.cve.org/CVERecord?id=CVE-2021-26869 Référence CVE CVE-2021-26870 https://www.cve.org/CVERecord?id=CVE-2021-26870 Référence CVE CVE-2021-26871 https://www.cve.org/CVERecord?id=

Official advisory ↗
JVN iPedia · Japanese · JVNDB-2021-001264Microsoft Windows 10 および Windows Server における権限を昇格される脆弱性

Microsoft Windows 10 および Windows Server には、Windows Win32k に不備があるため、権限を昇格される脆弱性が存在します。 本脆弱性は、CVE-2021-26863、CVE-2021-26875、CVE-2021-27077 とは異なる脆弱性です。

Official advisory ↗
JVN iPedia · Japanese · JVNDB-2021-001258複数の Microsoft Windows 製品における権限を昇格される脆弱性

複数の Microsoft Windows 製品には、Windows Win32k に不備があるため、権限を昇格される脆弱性が存在します。 本脆弱性は、CVE-2021-26863、CVE-2021-26900、CVE-2021-27077 とは異なる脆弱性です。

Official advisory ↗
JVN iPedia · Japanese · JVNDB-2021-001241複数の Microsoft Windows 製品における権限を昇格される脆弱性

複数の Microsoft Windows 製品には、Windows Win32k に不備があるため、権限を昇格される脆弱性が存在します。 本脆弱性は、CVE-2021-26863、CVE-2021-26875、CVE-2021-26900 とは異なる脆弱性です。

Official advisory ↗
JVN iPedia · Japanese · JVNDB-2021-001213Microsoft Windows 10 および Windows Server における権限を昇格される脆弱性

Microsoft Windows 10 および Windows Server には、Windows Win32k に不備があるため、権限を昇格される脆弱性が存在します。 本脆弱性は、CVE-2021-26875、CVE-2021-26900、CVE-2021-27077 とは異なる脆弱性です。

Official advisory ↗
KISA KrCERT/CC · Korean · KNVD-5282MS 3월 보안 위협에 따른 정기 보안 업데이트 권고

7074 Azure Sphere 미서명 코드 실행 취약성 Internet Explorer CVE-2021-27085 Internet Explorer 원격 코드 실행 취약성 CVE-2021-26411 Internet Explorer 메모리 손상 취약성 Microsoft ActiveX CVE-2021-26869 Windows ActiveX 설치 관리자 서비스 정보 유출 취약성 Microsoft Exchange Server CVE-2021-27065 Microsoft Exchange Server 원격 코드 실행 취약성 CVE-2021-26858 Microsoft Exchange Server 원격 코드 실행 취약성 CVE-2021-26857 Microsoft Exchange Server 원격 코드 실행 취약성 CVE-2021-26855 Microsoft Exchange Server 원격 코드 실행 취약성 Microsoft Graphics Component CVE-2021-27077 Windows Win32k 권한 상승 취약성 CVE-2021-26876 OpenType 글꼴 구문 분석 원격 코드 실행 취약성 CVE-2021-26875 Windows Win32k 권한 상승 취약성 CVE-2021-26868 Windows 그래픽 구성 요소 권한 상승 취약성 CVE-2021-26863 Windows Win32k 권한 상승 취약성 CVE-2021-26861 Windows 그래픽 구성 요소 원격 코드 실행 취약성 Microsoft Office CVE-2021-27059 Microsoft Office 원격 코드 실행 취약성 CVE-2021-27058 Microsoft Office 간편 실행 원격 코드 실행 취약성 CVE-2021-24108 Microsoft Office 원격 코드 실행 취약성 CVE-2021-27057 Microsoft Office 원격 코드 실행 취약성 CVE-2021-27054 Microsoft Excel 원격 코드 실행 취약성 CVE-2021-27053 Microsoft Excel 원격 코드 실행 취약성 CVE-2021-27056 Microsoft PowerPoint 원격 코드 실행 취약성 CVE-2021-27076 Microsoft SharePoint Server 원격 코드 실행 취약성 CVE-2021-27052 Microsoft SharePoint Server 정보 유출 취약성 CVE-2021-24104 Microsoft SharePoint 스푸핑 취약성 CVE-2021-27055 Microsoft Visio 보안 기능 우회 취약성 Microsoft Windows Codecs Library CVE-2021

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
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.
Action
Review the linked authoritative reference and apply the recorded fixed release appropriate to the affected product branch.
Workaround
No verified workaround is recorded. Limit untrusted access and use least privilege until authoritative guidance is available.
04

Evidence and provenance

Published 11 Mar 2021 · Last source change 19 Aug 2026, 16:30 UTC · CWE-269 · Improper Privilege Management

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 2026-08-14
European sourceENISA EUVD · EUVD-2021-13647
Product sourceCNA
Remediation sourceCVE/CNA references
CWE sourceNIST NVD
NVD statusNVD modified after enrichment

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

Material change intelligence

What changed after publication

View recent updates ↗
  1. Vendor guidanceAuthoritative vendor guidance changed: added remediation: portal.msrc.microsoft.com/CVE-2021-26863; removed patch: msrc.microsoft.com/CVE-2021-26863; removed remediation: msrc.microsoft.com/CVE-2021-26863.
    Before
    patch: msrc.microsoft.com/CVE-2021-26863 · patch: portal.msrc.microsoft.com/CVE-2021-26863 · remediation: msrc.microsoft.com/CVE-2021-26863
    After
    patch: portal.msrc.microsoft.com/CVE-2021-26863 · remediation: portal.msrc.microsoft.com/CVE-2021-26863
    portal.msrc.microsoft.com ↗
  2. Vendor guidanceAuthoritative vendor guidance changed: added patch: msrc.microsoft.com/CVE-2021-26863; added remediation: msrc.microsoft.com/CVE-2021-26863; removed remediation: portal.msrc.microsoft.com/CVE-2021-26863.
    Before
    patch: portal.msrc.microsoft.com/CVE-2021-26863 · remediation: portal.msrc.microsoft.com/CVE-2021-26863
    After
    patch: msrc.microsoft.com/CVE-2021-26863 · patch: portal.msrc.microsoft.com/CVE-2021-26863 · remediation: msrc.microsoft.com/CVE-2021-26863
    msrc.microsoft.com ↗
  3. Affected versionsThe structured affected or fixed version information changed.
    Before
    10.0.0 < publication · 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
    10.0.0 < 10.0.17134.2087; 10.0.17763.0 < 10.0.17763.1817; 10.0.0 < 10.0.17763.1817; 10.0.0 < 10.0.18363.1440; 10.0.0 < 10.0.19043.867 · 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 ↗
Material fields only · duplicate refreshes suppressed · history retained for the configured operational retention period
CVE published
Fixed release or patch reference recorded
ENISA EUVD · EUVD-2021-13647↗Patch or update reference↗CVE authority or vendor reference↗Public exploit 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-2021-26863 · cve.blacktree.nl