CVE-2021-34473 — Security Box Score

CVE · referencelatest edition

Reference page — cumulative record through Wednesday, August 19, 2026 UTC. Reference pages update as the archive grows; only dated daily editions are immutable pages of record.

CVE-2021-34473CRITICAL

Microsoft Exchange Server Remote Code Execution Vulnerability

  AV  AC  PR  UI  S  C  I  A   CVSS     EPSS    %ile   KEV
   N   L   N   N  U  H  H  N    9.1   1.0000   100.0   YES

AFFECTED
  Product                                              Versions   Fixed
  Microsoft Exchange Server 2013 Cumulative Update 23  15.00.0 –  —
  Microsoft Exchange Server 2016 Cumulative Update 19  15.01.0 –  —
  Microsoft Exchange Server 2016 Cumulative Update 20  15.01.0 –  —
  Microsoft Exchange Server 2019 Cumulative Update 8   15.02.0 –  —
  Microsoft Exchange Server 2019 Cumulative Update 9   15.02.0 –  —

TIMELINE
  Jun 9   Reserved by microsoft
  Nov 3   Added to CISA KEV, remediation due 2021-11-17
  Nov 3   Published (CNA: microsoft)
  Aug 10  EXPLOIT PUBLISHED — CVE-2021-34473 (Microsoft Exchange Server 2013 Cumulative Update 23). Public exploit reference added.

CWE-918 · CNA: microsoft · CVSS v3.1 · 5 references · NVD status: Analyzed · KEV due November 17, 2021

Description

Microsoft Exchange Server Remote Code Execution Vulnerability

Lifecycle

Complete event history — 4 events, chronological
Date	Event	Detail
June 9, 2021	Reserved	Reserved by microsoft
November 3, 2021	KEV ADDED	Added to CISA KEV, remediation due 2021-11-17
November 3, 2021	Published	Published (CNA: microsoft)
August 10, 2026	EXPLOIT PUBLISHED	EXPLOIT PUBLISHED — CVE-2021-34473 (Microsoft Exchange Server 2013 Cumulative Update 23). Public exploit reference added.

Affected

Affected products and packages — 5 rows
Vendor	Product / Package	Ecosystem	Version introduced	Fixed
Microsoft	Microsoft Exchange Server 2013 Cumulative Update 23	—	15.00.0	—
Microsoft	Microsoft Exchange Server 2016 Cumulative Update 19	—	15.01.0	—
Microsoft	Microsoft Exchange Server 2016 Cumulative Update 20	—	15.01.0	—
Microsoft	Microsoft Exchange Server 2019 Cumulative Update 8	—	15.02.0	—
Microsoft	Microsoft Exchange Server 2019 Cumulative Update 9	—	15.02.0	—

Weaknesses

CWE-918

References (5)

http://packetstormsecurity.com/files/163895/Microsoft-Exchange-ProxyShell-Remote-Code-Execution.html [Exploit, Third Party Advisory, VDB Entry]
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-34473 [Patch, Vendor Advisory]
https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-34473 [Patch, Vendor Advisory]
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-34473 [US Government Resource]
https://www.zerodayinitiative.com/advisories/ZDI-21-821/ [Third Party Advisory, VDB Entry]

Authoritative record: CVE-2021-34473 at cve.org

Vendors: microsoft

Weaknesses: CWE-918

About this page

This is a reference page, not a dated page of record. It assembles the complete lifecycle of CVE-2021-34473 from the CVE Program record, NVD enrichment, the CISA KEV catalog, EPSS, and OSV advisories. The box score's numbers (CVSS, EPSS, KEV status) are current as of Wednesday, August 19, 2026 UTC and are re-derived as the archive grows; only dated daily editions are immutable pages of record. The authoritative source for this identifier is cve.org.