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CVE-2021-34473

Published: Jul 14, 2021Updated: Oct 29, 2025 Sources: CVE List NVD BDUCWE-918
9.1CRITICAL
NVD MITRE
EPSS Score
100.0%
Top 0.0%
CISA KEV
Active Exploitation
Since Nov 3, 2021
Exploits
1 Known
Remediation
Patch Available

Description

Microsoft Exchange Server Remote Code Execution Vulnerability

No summary for this CVE yet.

CVSS Vector Breakdown

AV:NAC:LPR:NUI:NS:UC:HI:HA:N
Exploitability
AV:NAttack Vector
Network
AC:LAttack Complexity
Low
PR:NPrivileges Required
None
UI:NUser Interaction
None
Scope
S:UScope
Unchanged
Impact
C:HConfidentiality
High
I:HIntegrity
High
A:NAvailability
None
Open in CVSS calculator →

Weaknesses

CWE-918

Affected Products

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
Microsoft Exchange Server 2016 Cumulative Update 19Microsoft
On-premWeb App
Enterprise Software / itsm-monitoring
Microsoft Exchange Server 2019 Cumulative Update 8Microsoft
On-premWeb App
Enterprise Software / itsm-monitoring
microsoftcommercialUSOperating Systems
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
Am I actually vulnerable?2 Nuclei templates available — see how to check your systems. How to verify Rather we check it for you?We'll check your whole external perimeter for exposure — free. 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

2 techniques
Command and Control
Initial Access
View detailed technique mapping

References

https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-34473
portal.msrc.microsoft.com
https://www.zerodayinitiative.com/advisories/ZDI-21-821/
zerodayinitiative.com
http://packetstormsecurity.com/files/163895/Microsoft-Exchange-ProxyShell-Remote-Code-Execution.html
packetstormsecurity.com
and 4 more references View all →

Timeline

Published
Jul 14, 2021
Added to CISA KEV
Nov 3, 2021
Last Updated
Oct 29, 2025
News mentions
1

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