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Full vulnerability report · 2021
CVE-2021-42298High confidence

Microsoft Defender Remote Code Execution Vulnerability

Microsoft · Microsoft Malware Protection Engine

7.8HighCVSS 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 5.80% 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 Microsoft Malware Protection Engine 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-2021-29273

No EUVD known-exploited evidence

Microsoft Defender Remote Code Execution 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
7.8 · 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

Microsoft Defender Remote Code Execution Vulnerability

What

Microsoft Defender Remote Code Execution Vulnerability

Why

Untrusted data can cross into a code-evaluation path and be interpreted as executable instructions.

How

An attacker operating through local access may attempt exploitation without authentication after a user interaction. If successful, the issue may execute code or commands in the affected security context.

What

Microsoft Defender Remote Code Execution Vulnerability

Why

Untrusted data can cross into a code-evaluation path and be interpreted as executable instructions.

How

An attacker operating through local access may attempt exploitation without authentication after a user interaction. If successful, the issue may execute code or commands in the affected security context.

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 → Improper Control of Generation of Code ('Code Injection') → execute code or commands in the affected security context
Attack surface
Local
Privileges required
None: unauthenticated exploitation is possible
User interaction
Required interaction required
Attack complexity
Low: no specialised conditions are recorded
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-94 ↗

CWE-94: Improper Control of Generation of Code ('Code Injection'). The product constructs all or part of a code segment using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the syntax or behavior of the intended code segment.

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:N/UI:R/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.ACLowAttack complexity: No specialised conditions are required beyond attacker-controlled input.PRNonePrivileges required: The attacker does not need an account or existing privileges.UIRequiredUser interaction: Another user must perform an action for exploitation to succeed.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
After compromise, an attacker may use built-in shells, scripting engines, scheduled tasks and native network utilities for discovery, persistence or movement. This is a plausible LoTL path, not evidence that it has occurred for every attack.
UnauthenticatedRemote code executionCWE-94
A

Official authority intelligence

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

ENISA EUVD · EUVD-2021-29273Official EUVD mapping

Microsoft Defender Remote Code Execution Vulnerability

Official EUVD record ↗
Cyber Security Agency of Singapore · English · CSA-SB-20211117Security Bulletin 17 Nov 2021

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

Official advisory ↗
CERT-FR · French · CERTFR-2021-AVI-863Multiples vulnérabilités dans les produits Microsoft

d?id=CVE-2021-41368 Référence CVE CVE-2021-41372 https://www.cve.org/CVERecord?id=CVE-2021-41372 Référence CVE CVE-2021-41373 https://www.cve.org/CVERecord?id=CVE-2021-41373 Référence CVE CVE-2021-41374 https://www.cve.org/CVERecord?id=CVE-2021-41374 Référence CVE CVE-2021-41375 https://www.cve.org/CVERecord?id=CVE-2021-41375 Référence CVE CVE-2021-41376 https://www.cve.org/CVERecord?id=CVE-2021-41376 Référence CVE CVE-2021-42277 https://www.cve.org/CVERecord?id=CVE-2021-42277 Référence CVE CVE-2021-42292 https://www.cve.org/CVERecord?id=CVE-2021-42292 Référence CVE CVE-2021-42296 https://www.cve.org/CVERecord?id=CVE-2021-42296 Référence CVE CVE-2021-42298 https://www.cve.org/CVERecord?id=CVE-2021-42298 Référence CVE CVE-2021-42300 https://www.cve.org/CVERecord?id=CVE-2021-42300 Référence CVE CVE-2021-42301 https://www.cve.org/CVERecord?id=CVE-2021-42301 Référence CVE CVE-2021-42302 https://www.cve.org/CVERecord?id=CVE-2021-42302 Référence CVE CVE-2021-42303 https://www.cve.org/CVERecord?id=CVE-2021-42303 Référence CVE CVE-2021-42304 https://www.cve.org/CVERecord?id=CVE-2021-42304 Référence CVE CVE-2021-42305 https://www.cve.org/CVERecord?id=CVE-2021-42305 Référence CVE CVE-2021-42316 https://www.cve.org/CVERecord?id=CVE-2021-42316 Référence CVE CVE-2021-42319 https://www.cve.org/CVERecord?id=

Official advisory ↗
JVN iPedia · Japanese · JVNDB-2021-004377Microsoft Malware Protection Engine におけるリモートでコードを実行される脆弱性

Microsoft Malware Protection Engine には、Microsoft Defender に不備があるため、リモートでコードを実行される脆弱性が存在します。

Official advisory ↗
KISA KrCERT/CC · Korean · KNVD-5435MS 11월 보안 위협에 따른 정기 보안 업데이트 권고

Active Directory Domain Services Elevation of Privilege Vulnerability Windows Active Directory CVE-2021-42282 Active Directory Domain Services Elevation of Privilege Vulnerability Windows Active Directory CVE-2021-42278 Active Directory Domain Services Elevation of Privilege Vulnerability Windows COM CVE-2021-42275 Windows용 Microsoft COM 원격 코드 실행 취약성 Windows Core Shell CVE-2021-42286 Windows Core Shell SI Host Extension Framework for Composable Shell Elevation of Privilege Vulnerability Windows Cred SSProvider Protocol CVE-2021-41366 Credential Security Support Provider Protocol (CredSSP) Elevation of Privilege Vulnerability Windows Defender CVE-2021-42298 Microsoft Defender 원격 코드 실행 취약성 Windows Desktop Bridge CVE-2021-36957 Windows 데스크톱 브리지 권한 상승 취약성 Windows Diagnostic Hub CVE-2021-42277 진단 허브 표준 수집기 권한 상승 취약성 Windows Fastfat Driver CVE-2021-41377 Windows Fast FAT File System Driver Elevation of Privilege Vulnerability Windows Feedback Hub CVE-2021-42280 Windows 피드백 허브 권한 상승 취약성 Windows Hello CVE-2021-42288 Windows Hello 보안 기능 우회 취약성 Windows Installer CVE-2021-41379 Windows Installer 권한 상승 취약성 Windows Kernel CVE-2021-42285 Windows 커널 권한 상승 취약성 Windows NTFS CVE-2021-42283 NTFS 권한 상승 취약성 Windows NTFS CVE-2021-41378 Windows NTFS Remote Code Execution Vulnerability Windows NTFS CVE-2021-41370 NTF

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
Microsoft Malware Protection Engine: 1.1.0.0 < 1.1.18700.3
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 10 Nov 2021 · Last source change 19 Aug 2026, 16:27 UTC · CWE-94 · Improper Control of Generation of Code ('Code Injection')

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-2021-29273
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-2021-42298; removed patch: msrc.microsoft.com/CVE-2021-42298; removed remediation: msrc.microsoft.com/CVE-2021-42298.
    Before
    patch: msrc.microsoft.com/CVE-2021-42298 · patch: portal.msrc.microsoft.com/CVE-2021-42298 · remediation: msrc.microsoft.com/CVE-2021-42298
    After
    patch: portal.msrc.microsoft.com/CVE-2021-42298 · remediation: portal.msrc.microsoft.com/CVE-2021-42298
    portal.msrc.microsoft.com ↗
  2. Vendor guidanceAuthoritative vendor guidance changed: added patch: msrc.microsoft.com/CVE-2021-42298; added remediation: msrc.microsoft.com/CVE-2021-42298; removed remediation: portal.msrc.microsoft.com/CVE-2021-42298.
    Before
    patch: portal.msrc.microsoft.com/CVE-2021-42298 · remediation: portal.msrc.microsoft.com/CVE-2021-42298
    After
    patch: msrc.microsoft.com/CVE-2021-42298 · patch: portal.msrc.microsoft.com/CVE-2021-42298 · remediation: msrc.microsoft.com/CVE-2021-42298
    msrc.microsoft.com ↗
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-2021-29273↗Patch or update reference↗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-2021-42298 · cve.blacktree.nl