Skip to the content
The Update Bureau
Exchange Server Subscription Edition RTM Exchange Server Subscription Edition RTM Security update
Patch Tuesday

KB5074992

KB5074992: Security update for Exchange Server Subscription Edition RTM, February 2026. Spoofing vulnerability in Exchange addressed

In short

Resolves CVE-2026-21527, a spoofing vulnerability in Exchange Server.

Does it affect you? Applies to: Servers running Exchange Server Subscription Edition RTM. The update installs build 15.2.2562.37.

Build
15.2.2562.37
Servicing branch
RTM
Security
1 fixed
Restart
Required

What changes

Fix 1 change

Exchange Server

  • The update resolves a spoofing vulnerability in Exchange Server.1
    Resolves CVE-2026-21527.

Technical details

Data sheet · Security · Downloads · Components Click to collapse or expand

Data sheet

Released
2026-02-10
Classification
Security Updates
Type
Cumulative update
Servicing branch
RTM
Restart
Required
Replaces
KB5071876, KB5066366
Replaced by
KB5081755
VersionBuildChannel
SE 15.2.2562.37 General availability

Security

1 vulnerability fixed
1 important
VulnerabilitySeverityCVSS
CVE-2026-21527
Microsoft Exchange Server Spoofing Vulnerability
 Important 6.5

Updated components

1,006 files changed since the previous update for the same versions.

Top changed componentsFiles
Management and PowerShell121
Transport93
Client access (POP, IMAP, ActiveSync)33
Mailbox replication33
Search27
Compliance and eDiscovery25
Exchange Web Services and Autodiscover17
Outlook on the web8
Setup8

Sources

Updated
Cited passages from Microsoft's official notes (1)
  1. 1. This security update resolves vulnerabilities in Microsoft Exchange Server. support.microsoft.com
Checked automatically: 8 of 8 checks passed, 1 quoted passage · compared with Microsoft's page on Sep 26, 2026
  • Quotes found in the official pages: passed
  • Numbers found in the sources: passed
  • Vulnerabilities from the dossier only: passed
  • Links to allowed domains only: passed
  • Every official change covered: passed
  • Readable plain text: passed
  • Changes confirmed by the file list: passed
  • Sources agree: passed

A second AI read the text against the sources: correctness 5/5, clarity 5/5, completeness 5/5. How we work

Published by The Update Bureau. Written with AI from Microsoft's own documents, checked by rules and a second AI. How we work · Report a mistake