CVE-2021-34473

Microsoft Exchange Server Remote Code Execution Vulnerability

Score

CVSS 3.1 9.8 Critical

Status

Analyzed - secure@microsoft.com

Published

2021-07-14

Last modified

2026-08-10

Known exploited (CISA KEV)

since 2021-11-03, action due 2021-11-17: Apply updates per vendor instructions.

Weaknesses

CWE-918

Affected products

• Exchange Server (Microsoft)

References

• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-34473
• 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