This security update resolves vulnerabilities in Microsoft Exchange Server. To learn more about these vulnerabilities, see the following Common Vulnerabilities and Exposures (CVE):
- CVE-2026-55005 - Microsoft Exchange Server Remote Code Execution Vulnerability
- CVE-2026-55006 - Microsoft Exchange Server Elevation of Privilege Vulnerability
- CVE-2026-55008 - Microsoft Exchange Server Spoofing Vulnerability
- CVE-2026-55009 - Microsoft Exchange Server Elevation of Privilege Vulnerability
Known isssue
Exchange Server Health Checker
To verify that that the installation is successful, and check whether any additional actions are required, run the Exchange Server Health Checker.
Enabling Extended Protection in Exchange Server
To enable Extended Protection on Exchange-based servers, see Extended Protection enabled in Exchange Server (KB5017260).
How to get and install the update
Microsoft Download Center
You can get the standalone update package through the Microsoft Download Center.
- Microsoft Exchange Server Subscription Edition RTM SU8 - Download the package now.
More information
Security update deployment information
For deployment information about this update, see Deployments - Security Update Guide.
Security update replacement information
This security update replaces the following previously released updates:
File information
File hash information
| Update name | File name | SHA256 hash |
|---|---|---|
| Microsoft Exchange Server Subscription Edition RTM SU8 | ExchangeSubscriptionEdition-KB5103212-x64-en.exe | 01813B3DADA8195D43F9D67B375C94BBF67E2D4F6729C2ACD50596654A1A9EFF |
Hashes for additional languages
The hash tables for additional languages are available here:
- Microsoft Exchange Server Subscription Edition RTM SU8 (KB5103212) - Download the hashes now
Exchange Server file information
The English (United States) version of this update installs files that have the attributes that are listed in the following tables. The dates and times for these files are listed in Coordinated Universal Time (UTC). The dates and times for these files on your local computer are displayed in your local time together with your current daylight-saving time (DST) bias. Additionally, the dates and times may change when you perform certain operations on the files.
- Microsoft Exchange Server SE RTM SU8 - Download the file now
More information
For more information about the deployment of Exchange Server SE, see Release notes for Exchange Server SE.
For more information about the coexistence of Exchange Server SE and earlier versions of Exchange Server in the same environment, see Exchange Server SE system requirements.
For more information about other Exchange updates, see Exchange Server Updates: Build numbers and release dates.
Information about protection and security
Protect yourself online: Windows Security support
Learn how we guard against cyber threats: Microsoft Security