Back to CVE Browser

CVE-2021-34473

Known Exploited (CISA KEV)CRITICAL

9.1

CVSS Severity Score

EPSS Score87.1730%

EPSS Percentile95.71th

PublishedJul 14, 2021

Last ModifiedOct 29, 2025

Vulnerability Description

Microsoft Exchange Server Remote Code Execution Vulnerability

Affected Platforms (CPE)

📦

Microsoft

Exchange Server

= 2013

📦

Microsoft

Exchange Server

= 2016

📦

Microsoft

Exchange Server

= 2016

📦

Microsoft

Exchange Server

= 2019

📦

Microsoft

Exchange Server

= 2019

References & Advisories

🔗 http://packetstormsecurity.com/files/163895/Microsoft-Exchange-ProxyShell-Remote-Code-Execution.html

🔗 https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-34473

🔗 https://www.zerodayinitiative.com/advisories/ZDI-21-821/

🔗 http://packetstormsecurity.com/files/163895/Microsoft-Exchange-ProxyShell-Remote-Code-Execution.html

🔗 https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-34473

🔗 https://www.zerodayinitiative.com/advisories/ZDI-21-821/

🔗 https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-34473

Related Vulnerabilities

CVE-2004-084010.0

The SMTP (Simple Mail Transfer Protocol) component of Microsoft Windows XP 64-bit Edition, Windows Server 2003, Windows Server 200...

CVE-2006-662710.0

Integer overflow in the packed PE file parsing implementation in BitDefender products before 20060829, including Antivirus, Antivi...

CVE-2004-057410.0

The Network News Transfer Protocol (NNTP) component of Microsoft Windows NT Server 4.0, Windows 2000 Server, Windows Server 2003, ...

CVE-2007-021310.0

Microsoft Exchange Server 2000 SP3, 2003 SP1 and SP2, and 2007 does not properly decode certain MIME encoded e-mails, which allows...