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CVE-2021-34473

Microsoft Exchange Server Remote Code Execution Vulnerability

9.1 CriticalIn KEVPublic exploit

Microsoft Exchange Server Remote Code Execution Vulnerability

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
None
User interaction
None

What an attacker can affect

Confidentiality
High
Integrity
High
Availability
None

Exploit likelihood

100.0%Up 99.1 points since Jul 15, 2021
90%50%10%1%

What each source reports

CVE List Score used 9.1

Microsoft Exchange Server Remote Code Execution Vulnerability

Microsoft Exchange Server Remote Code Execution Vulnerability

Record
CVE-2021-34473
CVSS 3.1
9.1 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N/E:U/RL:O/RC:C
Weakness
CWE-918
Updated
2026-11-02
EUVDEUVD-2021-21128 9.1

Microsoft Exchange Server Remote Code Execution Vulnerability

Record
EUVD-2021-21128
CVSS 3.1
9.1 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N/E:U/RL:O/RC:C
Updated
2026-11-02
GitHub AdvisoriesGHSA-fgq9-p33g-xcfc 9.8

Microsoft Exchange Server Remote Code Execution Vulnerability This CVE ID is unique from CVE-2021...

Microsoft Exchange Server Remote Code Execution Vulnerability This CVE ID is unique from CVE-2021-31196, CVE-2021-31206.

Record
GHSA-fgq9-p33g-xcfc
CVSS 3.1
9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Weakness
CWE-918
Updated
2026-11-02
CISA KEV No score

Microsoft Exchange Server Remote Code Execution Vulnerability

Microsoft Exchange Server contains an unspecified vulnerability that allows for remote code execution.

Record
CVE-2021-34473
Weakness
CWE-918
Updated
2026-11-02
NVD 9.1

Microsoft Exchange Server Remote Code Execution Vulnerability

Record
CVE-2021-34473
CVSS 3.1
9.1 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
CVSS 3.1
9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CVSS 2.0
10.0 HighAV:N/AC:L/Au:N/C:C/I:C/A:C
Weakness
CWE-918
Updated
2026-11-02

Affected products

Public exploits

Links only. Every CVE stores no exploit code.

Public exploits
SourceLinkDate
MetasploitMicrosoft Exchange ProxyShell RCE2021-04-06
PoC in GitHubcyberheartmi9/Proxyshell-Scanner2021-08-10
PoC in GitHubRaouzRouik/CVE-2021-34473-scanner2021-08-11
PoC in GitHubp2-98/CVE-2021-344732021-08-16
PoC in GitHubhorizon3ai/proxyshell2021-09-04
PoC in GitHubje6k/CVE-2021-34473-Exchange-ProxyShell2021-11-22
PoC in GitHublearningsurface/ProxyShell-CVE-2021-34473.py2022-05-24
PoC in GitHubkh4sh3i/ProxyShell2022-06-29
PoC in GitHubipsBruno/CVE-2021-34473-NMAP-SCANNER2022-11-16
PoC in GitHubf4alireza/CVE2023-10-17
NucleiExchange Server - Remote Code Execution

History

History
RecordedChangedSources
exploitation, exploits
first indexedCVE List, EUVD, GitHub Advisories, CISA KEV, Metasploit, Nuclei, NVD, PoC in GitHub

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2021-34473 is a critical vulnerability (CVSS 9.1) in Microsoft Exchange Server, published July 14, 2021. CISA lists it as known to be exploited, since November 3, 2021. EUVD reports exploitation since November 3, 2021. Public exploit code exists. EPSS puts the chance of exploitation in the next 30 days at 100.0%, the 99th percentile. No source names a fixed version.

References

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