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-2021-31207

CVE-2021-31207MEDIUM

Microsoft Exchange Server Security Feature Bypass Vulnerability

  AV  AC  PR  UI  S  C  I  A   CVSS    EPSS    %ile   KEV
   N   H   H   N  U  H  H  H    6.6   .9978   100.0   YES

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

TIMELINE
  Apr 14  Reserved by microsoft
  May 11  Published (CNA: microsoft)
  Nov 3   Added to CISA KEV, remediation due 2021-11-17

CWE-434 · CNA: microsoft · CVSS v3.1 · 4 references · KEV due November 17, 2021

Description

Microsoft Exchange Server Security Feature Bypass Vulnerability

Lifecycle

Complete event history — 3 events, chronological
Date	Event	Detail
April 14, 2021	Reserved	Reserved by microsoft
May 11, 2021	Published	Published (CNA: microsoft)
November 3, 2021	KEV ADDED	Added to CISA KEV, remediation due 2021-11-17

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 2019 Cumulative Update 9	—	15.02.0	—
Microsoft	Microsoft Exchange Server 2016 Cumulative Update 20	—	15.01.0	—
Microsoft	Microsoft Exchange Server 2016 Cumulative Update 19	—	15.01.0	—
Microsoft	Microsoft Exchange Server 2019 Cumulative Update 8	—	15.02.0	—

Weaknesses

CWE-434

References (4)

http://packetstormsecurity.com/files/163895/Microsoft-Exchange-ProxyShell-Remote-Code-Execution.html [x_refsource_MISC]
https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-31207 [x_refsource_MISC]
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-31207 [government-resource]
https://www.zerodayinitiative.com/advisories/ZDI-21-819/ [x_refsource_MISC]

Authoritative record: CVE-2021-31207 at cve.org

Vendors: microsoft

Weaknesses: CWE-434

About this page

This is a reference page, not a dated page of record. It assembles the complete lifecycle of CVE-2021-31207 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.