Exchange Server SE SU10 V2 has been released

Hi All,

Yesterday, Microsoft has released the Exchange SE SU10 V2.

• Exchange Team Blog Released: September 2026 V2 Exchange Server Security Updates
• Description of version 2 of the security update for Microsoft Exchange Server Subscription Edition RTM October 2, 2026 (KB5129955)

It fixes the following CVEs

• CVE-2026-96940 - Microsoft Common Vulnerabilities and Exposures
• CVE-2026-55007 - Microsoft Common Vulnerabilities and Exposures
• CVE-2026-69355 - Microsoft Common Vulnerabilities and Exposures
• CVE-2026-69356 - Microsoft Common Vulnerabilities and Exposures
• CVE-2026-69361 - Microsoft Common Vulnerabilities and Exposures
• CVE-2026-69375 - Microsoft Common Vulnerabilities and Exposures
• CVE-2026-69378 - Microsoft Common Vulnerabilities and Exposures
• CVE-2026-69382 - Microsoft Common Vulnerabilities and Exposures
• CVE-2026-69641 - Microsoft Common Vulnerabilities and Exposures

Known issues in this update

• Published calendar (.ics) returns HTTP 500 for calendar applications
• Availability (free/busy) fails for delegated mailboxes in Exchange hybrid deployments that use Graph API only
• A ContentEngine deadlock occurs because of missing Korean WordBreaker rule files

Issues resolved in this update

• Wrapper messages appear in shared mailbox in hybrid environments after installing the June 2026 Security Update
• Availability (free/busy) fails for delegated mailboxes in Exchange hybrid deployments using Graph API only

The Process is simple: Install the SU and the run the Exchange Health Checker

You can download the Security Update here:

• Download Security Update for Exchange Server SE RTM SU10v2 (KB5129955)

Installation

Bevore starting the Installation, i check if there is a pending reboot with a PowerShell Script i’ve wrote

• Check for pending reboot with PowerShell

.\Check-PendingReboot.ps1

After a reboot everything looks fine

.\Check-PendingReboot.ps1

Let’s start the Installation

The Installation of the Security Update has successfully completed

Check the Version

Get-Command Exsetup.exe | ForEach-Object {$_.FileVersionInfo}

Check for Pending reboot

.\Check-PendingReboot.ps1

Healthchecker

Microsoft recommends to run the HealthChecker after each Installation. The HealthChecker can be downloaded here:

• HealthChecker

In the first run, the HealthChecker updates the Script

.\HealthChecker.ps1

Now we can run the HealthChecker - nothing worring was found

.\HealthChecker.ps1

Happy Exchange patching 😎

Regards
Andres Bohren