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Full vulnerability report · 2021
CVE-2021-43893High confidence

Windows Encrypting File System (EFS) Elevation of Privilege Vulnerability

Microsoft · Windows 10 Version 1809

7.5HighCVSS 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:High, unchanged from published severity.unchanged

Evidence used

  • No CISA KEV confirmation is currently recorded.
  • EPSS is 6.62% for the current model date.

Compensating controls

  • Validate the affected product branch and deploy the verified fixed release.
  • Restrict the affected network interface to trusted sources where business-safe.
  • Monitor vendor guidance and exploitation sources for a material change.

Verification

  1. Confirm that the asset runs Microsoft Windows 10 Version 1809 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-2021-30755

No EUVD known-exploited evidence

ENISA has published the identifier mapping but no EUVD description has been stored yet.

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
Not supplied in the stored EUVD record
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

Windows Encrypting File System (EFS) Elevation of Privilege Vulnerability

What

Windows Encrypting File System (EFS) Elevation of Privilege Vulnerability

Why

The product exposes a resource to the wrong control sphere, providing unintended actors with inappropriate access to the resource.

How

An attacker operating through a network path may attempt exploitation with low privileges. If successful, the issue may gain additional privileges.

What

Windows Encrypting File System (EFS) Elevation of Privilege Vulnerability

Why

The product exposes a resource to the wrong control sphere, providing unintended actors with inappropriate access to the resource.

How

An attacker operating through a network path 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.
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
a network path → Exposure of Resource to Wrong Sphere → gain additional privileges
Attack surface
Network
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-668 ↗

CWE-668: Exposure of Resource to Wrong Sphere. The product exposes a resource to the wrong control sphere, providing unintended actors with inappropriate access to the resource.

CVSS vector
?CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity.
CVSS:3.1/AV:N/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.

AVNetworkAttack vector: The vulnerable component can be reached over a network.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
No specific living-off-the-land technique is confirmed in the structured sources. Monitor normal administration tools for activity inconsistent with the affected service's baseline.
NetworkPrivilege escalationCWE-668
A

Official authority intelligence

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

BSI · German · WID-SEC-2025-2220Microsoft Windows und Microsoft Windows Server: Mehrere Schwachstellen

Ein entfernter, anonymer, authentisierter oder lokaler Angreifer kann mehrere Schwachstellen in Microsoft Windows und Microsoft Windows Server ausnutzen, um einen Denial of Service Zustand zu verursachen, seine Privilegien zu erhöhen, vertrauliche Informationen offenzulegen und beliebigen Code auszuführen.

Official advisory ↗
Cyber Security Agency of Singapore · English · CSA-SB-20211222Security Bulletin 22 Dec 2021

The Cyber Security Agency of Singapore included this CVE in its official Security Bulletin 22 Dec 2021, published on 22 December 2021. Open the linked bulletin for the product, severity and reference information published in that issue.

Official advisory ↗
CERT-FR · French · CERTFR-2021-AVI-959Multiples vulnérabilités dans Microsoft Windows

d?id=CVE-2021-43239 Référence CVE CVE-2021-43240 https://www.cve.org/CVERecord?id=CVE-2021-43240 Référence CVE CVE-2021-43244 https://www.cve.org/CVERecord?id=CVE-2021-43244 Référence CVE CVE-2021-43245 https://www.cve.org/CVERecord?id=CVE-2021-43245 Référence CVE CVE-2021-43246 https://www.cve.org/CVERecord?id=CVE-2021-43246 Référence CVE CVE-2021-43247 https://www.cve.org/CVERecord?id=CVE-2021-43247 Référence CVE CVE-2021-43248 https://www.cve.org/CVERecord?id=CVE-2021-43248 Référence CVE CVE-2021-43880 https://www.cve.org/CVERecord?id=CVE-2021-43880 Référence CVE CVE-2021-43883 https://www.cve.org/CVERecord?id=CVE-2021-43883 Référence CVE CVE-2021-43893 https://www.cve.org/CVERecord?id=CVE-2021-43893 Gestion détaillée du document le 15 décembre 2021 Version initiale Alertes Avis Bulletins d’actualités Mentions légales Conditions générales À propos Contact cyber.gouv.fr service-public.fr legifrance.gouv.fr info.gouv.fr france.fr info.gouv.fr/risques Premier Ministre / Secrétariat Général de la Défense et de la Sécurité Nationale / Agence nationale de la sécurité des systèmes d'information

Official advisory ↗
JVN iPedia · Japanese · JVNDB-2021-006055複数の Microsoft Windows における権限を昇格される脆弱性

複数の Microsoft Windows には、 Windows Encrypting File System (EFS) 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。

Official advisory ↗
KISA KrCERT/CC · Korean · KNVD-5468MS 12월 보안 위협에 따른 정기 보안 업데이트 권고

43908 Visual Studio Code 스푸핑 취약성 Visual Studio Code CVE-2021-43891 Visual Studio Code 원격 코드 실행 취약성 Visual Studio Code - WSL Extension CVE-2021-43907 Visual Studio Code WSL Extension Remote Code Execution Vulnerability Windows Common Log File System Driver CVE-2021-43226 Windows 공용 로그 파일 시스템 드라이버 권한 상승 취약성 Windows Common Log File System Driver CVE-2021-43224 Windows 공용 로그 파일 시스템 드라이버 정보 유출 취약성 Windows Common Log File System Driver CVE-2021-43207 Windows 공용 로그 파일 시스템 드라이버 권한 상승 취약성 Windows Digital TV Tuner CVE-2021-43245 Windows 디지털 TV 튜너 권한 상승 취약성 Windows DirectX CVE-2021-43219 DirectX 그래픽 커널 파일 서비스 거부 취약성 Windows Encrypting File System (EFS) CVE-2021-43893 Windows EFS(파일 시스템 암호화) 권한 상승 취약성 Windows Encrypting File System (EFS) CVE-2021-43217 Windows EFS(파일 시스템 암호화) 원격 코드 실행 취약성 Windows Event Tracing CVE-2021-43232 Windows 이벤트 추적 원격 코드 실행 취약성 Windows Installer CVE-2021-43883 Windows Installer 권한 상승 취약성 Windows Kernel CVE-2021-43244 Windows 커널 정보 유출 취약성 Windows Media CVE-2021-40441 Windows Media Center 권한 상승 취약성 Windows Mobile Device Management CVE-2021-43880 Windows 모바일 장치 관리 권한 상승 취약성 Windows Mobile Device Management CVE-2021-24084 Windows 모바일 장치 관리 정보 유출 취약성 Windows NTFS CVE-2021-43240 NTFS 설정 약식 이름 권한 상승 취약성 Windows NTFS CVE-2021-43231 Windows NTFS 권한 상승 취약성 Windows NTFS CVE-2021-43230 Window

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. If business-safe, reduce exposure to the affected interface and allow only trusted sources until authoritative guidance is available.
04

Evidence and provenance

Published 15 Dec 2021 · Last source change 4 Aug 2024, 04:10 UTC · CWE-668 · Exposure of Resource to Wrong Sphere

CVE recordCVE.org · 5.1
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-2021-30755
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 ↗

No material field changes have been recorded since change tracking began. Routine source refreshes and cosmetic edits are intentionally excluded.

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-2021-30755↗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-2021-43893 · cve.blacktree.nl