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CISA KEV · ACTIVELY EXPLOITED
MEDIUM severity

CVE-2026-45498 — Defender Antimalware Platform

MEDIUM

CVE-2026-45498 is a medium-severity (CVSS 4) Uncontrolled Resource Consumption vulnerability in microsoft defender antimalware platform. It is in CISA's Known Exploited Vulnerabilities catalog (added 2026-05-20) — treat it as actively exploited and patch now. A fix is available — see the affected versions and patch details below.

Microsoft Defender Denial of Service Vulnerability

Published
Updated
Affected
1 product
Patched
See advisory
Exploits
None indexed
Exploitation data as of Oct 21, 2026 · OSV.dev, NVD, CISA KEV, FIRST.org (EPSS)

Exploitation Status

Actively exploited in the wild

  • Confirmed by CISA's Known Exploited Vulnerabilities catalog on 2026-05-20. Federal agencies were required to remediate by 2026-06-03.

Exploitation and automatability from CISA (KEV catalog and SSVC triage) for CVE-2026-45498.

EPSS Exploitation Probability

via FIRST.org ↗
1.3%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs70th percentile — riskier than 70% of all scored CVEsHighest risk
0.00%27.2%54.4%81.6%4.1%63.1%63.1%1.3%1.3%Jun 26Sep 26Oct 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

CVE-2026-45498 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 395,308 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Description

Microsoft Defender Denial of Service Vulnerability

Affected Products

1 product · 1 configurations
Application
defender antimalware platformmicrosoft
< 4.18.26040.7
range

Detection & mitigation playbook

Vendor / appliance

  1. Detect

    Inventory every microsoft defender antimalware platform deployment and check each version against the affected-products list above.

  2. Fix

    Apply the microsoft defender antimalware platform security patch or hotfix for CVE-2026-45498 on the affected version, following the vendor advisory for your exact build.

  3. Workarounds

    Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service. Alongside that, restrict the management interface to trusted networks and apply the vendor's recommended configuration mitigations.

Frequently Asked Questions

Microsoft Defender Denial of Service Vulnerability
O3 Security · Runtime Protection

Is CVE-2026-45498 being exploited in your environment?

Detect and block the exploit chain at execution, on systems you cannot patch yet.

Protect my workloads How runtime protection works
CVE-2026-45498: Defender Antimalware Platform (KEV)