CVE intelligenceCISA KEVRansomware use

CVE-2021-31207

Microsoft Exchange Server Security Feature Bypass Vulnerability

Published May 11, 2021Sources checked Sep 12, 2026

6.6MEDIUMCVSS out of 10

What this means

Actively exploited

CISA lists CVE-2021-31207 in its Known Exploited Vulnerabilities catalog, which means exploitation has been observed. The entry applies to Microsoft Exchange Server.

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CISA KEVListedObserved exploitation

EPSS99.8%Estimated 30-day exploitation probability

Ransomware useReported by CISACISA KEV ransomware field

Threat actors1Source-linked actor relationships

Overview

What is CVE-2021-31207?

Microsoft Exchange Server Security Feature Bypass Vulnerability