CVE intelligenceCISA KEV

CVE-2026-45498

Microsoft Defender Denial of Service Vulnerability

Published May 20, 2026Sources checked Nov 12, 2026

7.5HIGHCVSS out of 10

What this means

Actively exploited

CISA lists CVE-2026-45498 in its Known Exploited Vulnerabilities catalog, which means exploitation has been observed. The entry applies to Microsoft Defender.

Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

Public exploit: Not collected.

Microsoft Security Response Center: Exploitation reported by Microsoft Security Response Center (2026-05-26)
Microsoft exploitation status: Exploited:Yes

What to do next

Remediation and response

Review the linked vendor advisory and apply the mitigation or fixed release for your affected product.

Microsoft Security Response Center guidance

Vendor revision: May 26, 2026

Release Notes

Vendor-listed releases

4.18.26040.7

CISA KEVListedObserved exploitation

EPSS63.1%Estimated 30-day exploitation probability

Ransomware useNot markedCISA KEV ransomware field

Threat actors0Source-linked actor relationships

Overview

What is CVE-2026-45498?

Microsoft Defender Denial of Service Vulnerability

Source: NVD

Reported activity: Microsoft exploitation status: Exploited:Yes
Microsoft Security Response Center · Published May 26, 2026

CISA says:Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.CISA catalog due date Jun 3, 2026