CVE-2021-31978: Microsoft Malware Protection Engine

Medium severity, CVSS 5.5. EPSS: 1.2% chance of exploitation in the next 30 days.

Microsoft Defender Denial of Service Vulnerability

Affected products

• Microsoft Malware Protection Engine: before 1.1.18200.3 (fixed in 1.1.18200.3)

Published 2021-06-08. Last modified 2026-06-17.