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

KB5103213

KB5103213: Security update for Exchange Server 2019 CU15, July 2026. Mail-server spoofing, code-execution and privilege flaws addressed

In short

Addresses 11 vulnerabilities in Exchange Server, including one Critical flaw. It is available only to organizations enrolled in the Extended Security Update program.

Does it affect you? Applies to: Organizations enrolled in the Extended Security Update program that run Exchange Server 2019 CU15. Exchange Server 2019 has reached end of support.

Build
15.2.1748.48
Servicing branch
CU15
Security
11 fixed · 1 critical

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 4 changes

Exchange Server

4 items
  • Closes a remote code execution vulnerability in Exchange Server.1
    CVE-2026-55005.
  • Closes an elevation of privilege vulnerability in Exchange Server.2
    CVE-2026-55006.
  • Closes a spoofing vulnerability in Exchange Server.3
    CVE-2026-55008; Critical severity.
  • Closes an elevation of privilege vulnerability in Exchange Server.4
    CVE-2026-55009.

Technical details

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

Data sheet

Released
2026-07-14
Classification
Security Updates
Type
Cumulative update
Servicing branch
CU15
Replaces
KB5094140
Replaced by
KB5121574
VersionBuildChannel
2019 15.2.1748.48 General availability

Security

11 vulnerabilities fixed
1 critical 10 important
VulnerabilitySeverityCVSS
CVE-2026-55008
Microsoft Exchange Server Spoofing Vulnerability
 Critical 9.6
CVE-2026-45504
Microsoft Exchange Server Elevation of Privilege Vulnerability
 Important 8.8
CVE-2026-55005
Microsoft Exchange Server Remote Code Execution Vulnerability
 Important 8.8
CVE-2026-45503
Microsoft Exchange Server Information Disclosure Vulnerability
 Important 8.1
CVE-2026-47631
Microsoft Exchange Server Spoofing Vulnerability
 Important 8.1
CVE-2026-55006
Microsoft Exchange Server Elevation of Privilege Vulnerability
 Important 7.8
CVE-2026-55009
Microsoft Exchange Server Elevation of Privilege Vulnerability
 Important 7.8
CVE-2026-45583
Microsoft Exchange Server Remote Code Execution Vulnerability
 Important 7.5
CVE-2026-45501
Microsoft Exchange Server Spoofing Vulnerability
 Important 6.5
CVE-2026-45500
Microsoft Exchange Server Spoofing Vulnerability
 Important 6.1
CVE-2026-45502
Microsoft Exchange Server Information Disclosure Vulnerability
 Important 5.0

Updated components

1,349 files changed since the previous update for the same versions.

Top changed componentsFiles
Management and PowerShell124
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 (4)
  1. 1. - [CVE-2026-55005 - Microsoft Exchange Server Remote Code Execution Vulnerability] support.microsoft.com
  2. 2. - [CVE-2026-55006 - Microsoft Exchange Server Elevation of Privilege Vulnerability] support.microsoft.com
  3. 3. - [CVE-2026-55008 - Microsoft Exchange Server Spoofing Vulnerability] support.microsoft.com
  4. 4. - [CVE-2026-55009 - Microsoft Exchange Server Elevation of Privilege Vulnerability] support.microsoft.com
Checked automatically: 8 of 8 checks passed, 4 quoted passages · 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 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