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Full vulnerability report · 2026
CVE-2026-45498High confidence

Microsoft Defender Denial of Service Vulnerability

Microsoft · Defender

4.0MediumCVSS 3.1
Recommended action
Patch now

CISA confirms exploitation in the wild and lists 2026-06-03 as the remediation due date.

Patch available
R
Operational reassessment

Published severity in operational context

Open reassessment dashboard →
Published severityMediumOperational priority:Critical, raised 2 bands.upgradedsince 20 May 2026

Evidence used

  • CISA confirms exploitation in the wild.
  • EPSS is 1.27% 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 Defender 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 3 daysRemediation target: Within 90 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-2026-31102

CISA KEV mirrored by ENISA

Microsoft Defender Denial of Service Vulnerability

EUVD state
Present in the current official mapping
Known exploitation
Recorded by ENISA since 20 May 2026. Evidence sources: cisa_kev.
ENISA score
4.0 · CVSS 3.1
Advisory evidence
2 linked advisory records
Recommended actionPatch now

CISA confirms exploitation in the wild and lists 2026-06-03 as the remediation due date.

Patch available
01

What, why and how

Microsoft Defender contains an unspecified vulnerability that allows for denial of service.

What

Microsoft Defender contains an unspecified vulnerability that allows for denial of service.

Why

The product does not properly control the allocation and maintenance of a limited resource.

How

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

What

Microsoft Defender contains an unspecified vulnerability that allows for denial of service.

Why

The product does not properly control the allocation and maintenance of a limited resource.

How

An attacker operating through local access may attempt exploitation without authentication or 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.
Confirmed in the wild

CISA added this CVE to its Known Exploited Vulnerabilities catalogue on 2026-05-20.

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 → Uncontrolled Resource Consumption → disrupt the affected service
Attack surface
Local
Privileges required
None: unauthenticated exploitation is possible
User interaction
None
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-400 ↗

CWE-400: Uncontrolled Resource Consumption. The product does not properly control the allocation and maintenance of a limited resource.

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:N/S:U/C:N/I:N/A:L/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.UINoneUser interaction: No action by another user is required.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.ALowAvailability impact: A successful attack can cause a limited 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 serviceCWE-400CISA KEV
A

Official authority intelligence

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

ENISA EUVD · EUVD-2026-31102Known-exploited evidence recorded

Microsoft Defender Denial of Service Vulnerability

Official EUVD record ↗
BSI · German · WID-SEC-2026-1603Microsoft Defender und Malware Protection Engine: Mehrere Schwachstellen

Ein Angreifer kann mehrere Schwachstellen in Microsoft Defender und Microsoft Malware Protection Engine ausnutzen, um seine Privilegien zu erhöhen, um beliebigen Code auszuführen und um einen Denial of Service Zustand herbeizuführen.

Official advisory ↗
Canadian Centre for Cyber Security · English · AV26-489Microsoft security advisory (AV26-489)

On May 18 and 19, 2026, Microsoft published security advisories to address vulnerabilities, including some critical ones, in the following products: On May 20, 2026, Cybersecurity and Infrastructure Security Agency (CISA) added CVE-2026-41091 and CVE-2026-45498 to their Known Exploited Vulnerabilities (KEV) Database.

Official advisory ↗
CERT-FR · French · CERTFR-2026-AVI-0623Multiples vulnérabilités dans les produits Microsoft

De multiples vulnérabilités ont été découvertes dans les produits Microsoft. Certaines d'entre elles permettent à un attaquant de provoquer une exécution de code arbitraire à distance, une élévation de privilèges et un déni de service. Microsoft indique que les vulnérabilités CVE-2026-41091 et CVE-2026-45498 sont activement exploitées.

Official advisory ↗
JVN iPedia · Japanese · JVNDB-2026-016663マイクロソフトのMicrosoft Defender Antimalware Platformにおけるリソースの枯渇に関する脆弱性

Microsoft Defender においてサービス拒否の脆弱性が存在します。

Official advisory ↗
KISA KrCERT/CC · Korean · KNVD-6797美 CISA 발표 주요 Exploit 정보공유(Update. 2026-05-20)

Microsoft Defender Denial of Service Vulnerability

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 Defender Antimalware Platform: 4.0.0.0 < 4.18.26040.7
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 20 May 2026 · Last source change 10 Aug 2026, 15:13 UTC · CWE-400 · Uncontrolled Resource Consumption

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-2026-31102
Product sourceCISA KEV
Remediation sourceCVE/CNA references
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. BlackTree coverageBlackTree article coverage changed from no BlackTree article to 1 BlackTree article.
    Before
    no BlackTree article
    After
    1 BlackTree article
    BlackTree editorial ↗
  2. Vendor guidanceAuthoritative vendor guidance changed: removed remediation: cyber.gc.ca/microsoft-security-advisory-av26-489.
    Before
    remediation: cyber.gc.ca/microsoft-security-advisory-av26-489 · vendor advisory: msrc.microsoft.com/CVE-2026-45498
    After
    vendor advisory: msrc.microsoft.com/CVE-2026-45498
    secure@microsoft.com ↗
  3. Remediation statusRemediation status changed from Mitigation available to Awaiting fix.
    Before
    Mitigation available
    After
    Awaiting fix
    secure@microsoft.com ↗
  4. Affected versionsThe structured affected or fixed version information changed.
    Before
    4.0.0.0 < 4.18.26040.7 · Fixed: No fixed version is explicitly recorded in the structured CVE data.
    After
    Microsoft Defender Antimalware Platform: 4.0.0.0 < 4.18.26040.7 · Fixed: No fixed version is explicitly recorded in the structured CVE data.
    CNA ↗
  5. Remediation statusRemediation status changed from Awaiting fix to Mitigation available.
    Before
    Awaiting fix
    After
    Mitigation available
    Canadian Centre for Cyber Security ↗
Material fields only · duplicate refreshes suppressed · history retained for the configured operational retention period
CVE published
Added to CISA KEV
ENISA EUVD · EUVD-2026-31102↗CISA KEV record↗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-2026-45498 · cve.blacktree.nl