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Full vulnerability report · 2021
CVE-2021-28326High confidence

Windows AppX Deployment Server Denial of Service Vulnerability

Microsoft · Windows 10 Version 1803

5.5MediumCVSS 3.1
Recommended action
Scheduled

Medium technical severity with no CISA KEV confirmation; remediate through the normal risk-based patch cycle unless local exposure raises the priority.

Patch available
R
Operational reassessment

Published severity in operational context

Open reassessment dashboard →
Published severityMediumOperational priority:Medium, unchanged from published severity.unchanged

Evidence used

  • No CISA KEV confirmation is currently recorded.
  • EPSS is 0.98% 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 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: 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.

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-2021-15011

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 actionScheduled

Medium technical severity with no CISA KEV confirmation; remediate through the normal risk-based patch cycle unless local exposure raises the priority.

Patch available
01

What, why and how

Windows AppX Deployment Server Denial of Service Vulnerability

What

Windows AppX Deployment Server Denial of Service Vulnerability

Why

The current structured CVE record identifies a security weakness, but the root cause requires confirmation in the linked vendor material.

How

An attacker operating through local access may attempt exploitation without authentication after a user interaction. If successful, the issue may disrupt the affected service.

What

Windows AppX Deployment Server Denial of Service Vulnerability

Why

The current structured CVE record identifies a security weakness, but the root cause requires confirmation in the linked vendor material.

How

An attacker operating through local access may attempt exploitation without authentication after a user interaction. If successful, the issue may disrupt the affected service.

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 → vulnerable operation → disrupt the affected service
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.
CWE not yet assigned
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:N/I:N/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.CNoneConfidentiality impact: No direct loss is represented by this metric.INoneIntegrity impact: No direct loss is represented by this metric.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.
UnauthenticatedDenial of service
A

Official authority intelligence

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

Cyber Security Agency of Singapore · English · CSA-SB-20210414Security Bulletin 14 Apr 2021

The Cyber Security Agency of Singapore included this CVE in its official Security Bulletin 14 Apr 2021, published on 14 April 2021. Open the linked bulletin for the product, severity and reference information published in that issue.

Official advisory ↗
CERT-FR · French · CERTFR-2021-AVI-261Multiples vulnérabilités dans Microsoft Windows

d?id=CVE-2021-28317 Référence CVE CVE-2021-28318 https://www.cve.org/CVERecord?id=CVE-2021-28318 Référence CVE CVE-2021-28319 https://www.cve.org/CVERecord?id=CVE-2021-28319 Référence CVE CVE-2021-28320 https://www.cve.org/CVERecord?id=CVE-2021-28320 Référence CVE CVE-2021-28321 https://www.cve.org/CVERecord?id=CVE-2021-28321 Référence CVE CVE-2021-28322 https://www.cve.org/CVERecord?id=CVE-2021-28322 Référence CVE CVE-2021-28323 https://www.cve.org/CVERecord?id=CVE-2021-28323 Référence CVE CVE-2021-28324 https://www.cve.org/CVERecord?id=CVE-2021-28324 Référence CVE CVE-2021-28325 https://www.cve.org/CVERecord?id=CVE-2021-28325 Référence CVE CVE-2021-28326 https://www.cve.org/CVERecord?id=CVE-2021-28326 Référence CVE CVE-2021-28327 https://www.cve.org/CVERecord?id=CVE-2021-28327 Référence CVE CVE-2021-28328 https://www.cve.org/CVERecord?id=CVE-2021-28328 Référence CVE CVE-2021-28329 https://www.cve.org/CVERecord?id=CVE-2021-28329 Référence CVE CVE-2021-28330 https://www.cve.org/CVERecord?id=CVE-2021-28330 Référence CVE CVE-2021-28331 https://www.cve.org/CVERecord?id=CVE-2021-28331 Référence CVE CVE-2021-28332 https://www.cve.org/CVERecord?id=CVE-2021-28332 Référence CVE CVE-2021-28333 https://www.cve.org/CVERecord?id=CVE-2021-28333 Référence CVE CVE-2021-28334 https://www.cve.org/CVERecord?id=

Official advisory ↗
JVN iPedia · Japanese · JVNDB-2021-001450Microsoft Windows 10 および Windows Server におけるサービス運用妨害 (DoS) の脆弱性

Microsoft Windows 10 および Windows Server には、Windows AppX Deployment Server に不備があるため、サービス運用妨害 (DoS) の脆弱性が存在します。

Official advisory ↗
KISA KrCERT/CC · Korean · KNVD-5297MS 4월 보안 위협에 따른 정기 보안 업데이트 권고

-2021-28471 Visual Studio Code용 원격 개발 확장 원격 코드 실행 취약성 Visual Studio Code CVE-2021-28469 Visual Studio Code 원격 코드 실행 취약성 Visual Studio Code CVE-2021-28457 Visual Studio Code 원격 코드 실행 취약성 Visual Studio Code - GitHub Pull Requests and Issues Extension CVE-2021-28470 Visual Studio Code GitHub 끌어오기 요청 및 문제 확장 원격 코드 실행 취약성 Visual Studio Code - Kubernetes Tools CVE-2021-28448 Visual Studio Code Kubernetes 도구 원격 코드 실행 취약성 Visual Studio Code - Maven for Java Extension CVE-2021-28472 Java용 Visual Studio Code Maven 확장 원격 코드 실행 취약성 Windows Application Compatibility Cache CVE-2021-28311 Windows 응용 프로그램 호환성 캐시 서비스 거부 취약성 Windows AppX Deployment Extensions CVE-2021-28326 Windows AppX 배포 서버 서비스 거부 취약성 Windows Console Driver CVE-2021-28443 Windows 콘솔 드라이버 서비스 거부 취약성 Windows Console Driver CVE-2021-28438 Windows 콘솔 드라이버 서비스 거부 취약성 Windows Diagnostic Hub CVE-2021-28322 진단 허브 표준 수집기 서비스 권한 상승 취약성 Windows Diagnostic Hub CVE-2021-28321 진단 허브 표준 수집기 서비스 권한 상승 취약성 Windows Diagnostic Hub CVE-2021-28313 진단 허브 표준 수집기 서비스 권한 상승 취약성 Windows Early Launch Antimalware Driver CVE-2021-28447 Windows 조기 실행 맬웨어 방지 드라이버 보안 기능 우회 취약성 Windows ELAM CVE-2021-27094 Windows 조기 실행 맬웨어 방지 드라이버 보안 기능 우회 취약성 Windows Event Tracing CVE-2021-28435 Windows 이벤트 추적 정보 유출 취약성 Windows Event Tracing CVE-2021-27088 Windows 이벤트 추적 권한 상승 취약성 Windows I

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 13 Apr 2021 · Last source change 3 Aug 2024, 21:40 UTC · CWE not yet assigned

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-2021-15011
Product sourceCNA
Remediation sourceCVE/CNA references
CWE sourceUnavailable
NVD statusNVD modified after enrichment

Missing structured fields: CWE classification. Missing data is not evidence of low risk; review the primary advisory.

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-2021-15011↗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-2021-28326 · cve.blacktree.nl