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CVE-2021-31207

Published: May 11, 2021Updated: Oct 30, 2025 Sources: CVE List NVD BDUCWE-434
6.6MEDIUM
NVD MITRE
EPSS Score
99.8%
Top 0.0%
CISA KEV
Active Exploitation
Since Nov 3, 2021
Exploits
1 Known
Remediation
Patch Available

Description

Microsoft Exchange Server Security Feature Bypass Vulnerability

No summary for this CVE yet.

CVSS Vector Breakdown

AV:NAC:HPR:HUI:NS:UC:HI:HA:H
Exploitability
AV:NAttack Vector
Network
AC:HAttack Complexity
High
PR:HPrivileges Required
High
UI:NUser Interaction
None
Scope
S:UScope
Unchanged
Impact
C:HConfidentiality
High
I:HIntegrity
High
A:HAvailability
High
Open in CVSS calculator →

Weaknesses

CWE-434

Affected Products

exchange servermicrosoft
On-prem
Operating Systems / windows
Microsoft Exchange ServerMicrosoft Corp
On-prem
Operating Systems
Microsoft Exchange Server 2013 Cumulative Update 23Microsoft
On-prem
Enterprise Software / itsm-monitoring
Microsoft Exchange Server 2019 Cumulative Update 9Microsoft
On-premWeb App
Enterprise Software / itsm-monitoring
Microsoft Exchange Server 2016 Cumulative Update 20Microsoft
On-premWeb App
Enterprise Software / itsm-monitoring
microsoftcommercialUSOperating Systems
microsoft corpcommercialUSOperating Systemsaka microsoft corporation
and 2 more affected products View all →

Exploitability

CISA Known Exploited Vulnerability
Added to KEV:Nov 3, 2021
Remediation due:Nov 17, 2021
Ransomware:Known ransomware use

Required action: Apply updates per vendor instructions.

1 exploit source identified

Exploit details including PoC links, Metasploit modules, and scanner templates are available after registration.

View exploit details
Official Patch Available
No detection template yetWe can run the check for you — a free external exposure review, no install. Check my exposure

Attack Graph

Products CVE Techniques Tactics

Click technique nodes to view MITRE ATT&CK details. Scroll to zoom, drag to pan.

MITRE ATT&CK

3 techniques
Command and Control
Initial Access
Persistence
View detailed technique mapping

References

http://packetstormsecurity.com/files/163895/Microsoft-Exchange-ProxyShell-Remote-Code-Execution.html
packetstormsecurity.com
https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-31207
portal.msrc.microsoft.com
https://www.zerodayinitiative.com/advisories/ZDI-21-819/
zerodayinitiative.com
and 5 more references View all →

Timeline

Published
May 11, 2021
Added to CISA KEV
Nov 3, 2021
Last Updated
Oct 30, 2025

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