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Exchange Server 2019 CU15 Exchange Server 2019 CU15 ESU only Security update
Patch Tuesday

KB5063221

KB5063221: Security update for Exchange Server 2019 CU15, August 2025. Four vulnerabilities addressed; eDiscovery and app-pool issues fixed

In short

The update addresses four Important vulnerabilities and fixes eDiscovery exports, unresponsive application pools after MSIPC is enabled, and incorrect ACE changes through Outlook public-folder management.

Does it affect you? Applies to: Exchange Server 2019 CU15 x64 servers at organizations enrolled in the Extended Security Update program.

Build
15.2.1748.36
Servicing branch
CU15
Security
4 fixed

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

Fixes 3 changes

eDiscovery

  • eDiscovery search results can be exported to a discovery mailbox again.1
    Fixes Exchange Server failing to export eDiscovery search results to a discovery mailbox.

Application pools

  • Application pools no longer stop responding and affect performance after MSIPC is enabled.2
    Fixes application pools stopping and performance being affected after MSIPC is enabled.

Public folder management

  • Outlook no longer modifies the incorrect ACE through public folder management.3
    Fixes modification of an incorrect ACE through public folder management in Outlook.

Technical details

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

Data sheet

Released
2025-08-12
Classification
Security Updates
Type
Cumulative update
Servicing branch
CU15
Replaces
KB5057651
Replaced by
KB5066372
VersionBuildChannel
2019 15.2.1748.36 General availability

Security

4 vulnerabilities fixed
4 important
VulnerabilitySeverityCVSS
CVE-2025-33051
Microsoft Exchange Server Information Disclosure Vulnerability
 Important 7.5
CVE-2025-25005
Microsoft Exchange Server Tampering Vulnerability
 Important 6.5
CVE-2025-25006
Microsoft Exchange Server Spoofing Vulnerability
 Important 5.3
CVE-2025-25007
Microsoft Exchange Server Spoofing Vulnerability
 Important 5.3

Sources

Updated
Cited passages from Microsoft's official notes (3)
  1. 1. Exchange Server fails to export eDiscovery search results to a discovery mailbox support.microsoft.com
  2. 2. Application pools stop responding and performance is affected after MSIPC is enabled support.microsoft.com
  3. 3. Incorrect ACE is modified through public folder management in Outlook support.microsoft.com
Checked automatically: 7 of 8 checks passed, 3 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: not passed

A second AI read the text against the sources: correctness 5/5, clarity 4/5, 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