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Reference page — cumulative record through Sunday, October 4, 2026 UTC. Reference pages update as the archive grows; only dated daily editions are immutable pages of record.

CVE-2021-42321

CVE-2021-42321HIGH
Microsoft Exchange Server Remote Code Execution Vulnerability
  AV  AC  PR  UI  S  C  I  A   CVSS    EPSS   %ile   KEV
   N   L   L   N  U  H  H  H    8.8   .9174   99.8   YES
AFFECTED
  Product                                              Versions   Fixed
  Microsoft Exchange Server 2016 Cumulative Update 21  15.01.0 –  —
  Microsoft Exchange Server 2016 Cumulative Update 22  15.0.0 –   —
  Microsoft Exchange Server 2019 Cumulative Update 10  15.02.0 –  —
  Microsoft Exchange Server 2019 Cumulative Update 11  15.02.0 –  —
TIMELINE
  Oct 12  Reserved by microsoft
  Nov 17  Added to CISA KEV, remediation due 2021-12-01
  Nov 17  Published (CNA: microsoft)
  Aug 19  EXPLOIT PUBLISHED — CVE-2021-42321 (Microsoft Exchange Server 2016 Cumulative Update 21). Public exploit reference added.
CNA: microsoft · CVSS v3.1 · 5 references · NVD status: Analyzed · KEV due December 1, 2021

Description

Microsoft Exchange Server Remote Code Execution Vulnerability

Lifecycle

Complete event history — 4 events, chronological
DateEventDetail
October 12, 2021ReservedReserved by microsoft
November 17, 2021KEV ADDEDAdded to CISA KEV, remediation due 2021-12-01
November 17, 2021PublishedPublished (CNA: microsoft)
August 19, 2026EXPLOIT PUBLISHEDEXPLOIT PUBLISHED — CVE-2021-42321 (Microsoft Exchange Server 2016 Cumulative Update 21). Public exploit reference added.

Affected

Affected products and packages — 4 rows
VendorProduct / PackageEcosystemVersion introducedFixed
MicrosoftMicrosoft Exchange Server 2016 Cumulative Update 21—15.01.0—
MicrosoftMicrosoft Exchange Server 2016 Cumulative Update 22—15.0.0—
MicrosoftMicrosoft Exchange Server 2019 Cumulative Update 10—15.02.0—
MicrosoftMicrosoft Exchange Server 2019 Cumulative Update 11—15.02.0—

References (5)

Related

Authoritative record: CVE-2021-42321 at cve.org

Vendors: microsoft

About this page

This is a reference page, not a dated page of record. It assembles the complete lifecycle of CVE-2021-42321 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 Sunday, October 4, 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.