Overview
What is CVE-2021-31207?
Microsoft Exchange Server Security Feature Bypass Vulnerability
Source: NVD
CISA says:Apply updates per vendor instructions.CISA catalog due date Nov 17, 2021
CVE intelligenceCISA KEVRansomware use
CVE-2021-31207
Microsoft Exchange Server Security Feature Bypass Vulnerability
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.
- Apply updates per vendor instructions.
Public exploit: Cataloged public exploit.
- Rapid7 Metasploit: Microsoft Exchange ProxyShell RCE (2026-09-23 21:40:29.350562+00)
Rapid7 catalogs an exploit module for this CVE. Module availability does not establish exploitation in the wild or applicability to your environment.
CISA KEVListedObserved exploitation
EPSS99.8%Estimated 30-day exploitation probability
Ransomware useReported by CISACISA KEV ransomware field
Threat actors1Source-linked actor relationships