CVE-2021-42321: Microsoft Exchange Server Remote Code Execution Vulnerability

High severity, CVSS 8.8. Actively exploited: in CISA KEV since 2021-11-17. EPSS: 91.7% chance of exploitation in the next 30 days.

Microsoft Exchange Server Remote Code Execution Vulnerability

Affected products

• Microsoft Exchange Server: version 2016 only; version 2019 only

Published 2021-11-10. Last modified 2026-08-19.