Skip to the content
The Update Bureau
Exchange Server 2019 CU15 Exchange Server 2019 CU15 ESU only Security update
Patch Tuesday

KB5066367

KB5066367: Security update for Exchange Server 2019 CU15, October 2025. Three vulnerabilities fixed; Auth Certificate export no longer supported

In short

The update fixes three important vulnerabilities and makes Auth Certificate export through an Exchange cmdlet no longer supported.

Does it affect you? Applies to: Organizations in the Extended Security Update (ESU) program running Exchange Server 2019 CU15.

Build
15.2.1748.39
Servicing branch
CU15
Security
3 fixed
Review notes Additional details from the official release notes (1) Read note
  • What to do Microsoft says to follow the instructions in the MSRC article to address the vulnerability.

The official sources are linked at the end of the page.

For servers running Cumulative Update 15: each cumulative update gets its own update. Support for this version ended on October 14, 2025: Microsoft releases this update only to organizations enrolled in the Extended Security Update (ESU) program, not through Microsoft Update. The others should move to Exchange Server Subscription Edition. Which version am I on?

What changes

Fix 1 change

Security

  • The update fixes three vulnerabilities in Exchange Server.1
    Addresses CVE-2025-59249 and CVE-2025-53782 (elevation of privilege), and CVE-2025-59248 (spoofing).

Removal 1 change

Auth Certificate export

  • Exporting the Auth Certificate through an Exchange cmdlet is no longer supported.2

Technical details

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

Data sheet

Released
2025-10-14
Classification
Security Updates
Type
Cumulative update
Servicing branch
CU15
Replaces
KB5066372, KB5063221
Replaced by
KB5071875
VersionBuildChannel
2019 15.2.1748.39 General availability

Security

3 vulnerabilities fixed
3 important
VulnerabilitySeverityCVSS
CVE-2025-59249
Microsoft Exchange Server Elevation of Privilege Vulnerability
 Important 8.8
CVE-2025-53782
Microsoft Exchange Server Elevation of Privilege Vulnerability
 Important 8.4
CVE-2025-59248
Microsoft Exchange Server Spoofing Vulnerability
 Important 7.5

Updated components

1,025 files changed since the previous update for the same versions.

Top changed componentsFiles
Management and PowerShell138
Transport93
Client access (POP, IMAP, ActiveSync)33
Mailbox replication33
Search27
Compliance and eDiscovery26
Exchange Web Services and Autodiscover17
Outlook on the web8
Setup8

Sources

Updated
Cited passages from Microsoft's official notes (2)
  1. 1. This security update rollup resolves vulnerabilities in Microsoft Exchange Server. support.microsoft.com
  2. 2. Auth Certificate export through Exchange cmdlet is no longer supported support.microsoft.com
Checked automatically: 8 of 8 checks passed, 2 quoted passages · compared with Microsoft's page on Oct 20, 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 4/5, clarity 4/5, completeness 3/5. 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