Exchange 2016 CU22 vs CU23: Security Update Requirements
Question details
The user needs to determine if Exchange Server 2016 security updates for Cumulative Update 23 (CU23) apply to CU22, and whether an upgrade is mandatory.
- Product
- Microsoft Exchange Server 2016
- Device & OS
- not provided
- Scenario
- Evaluating Exchange Server upgrade paths to ensure continued receipt of critical security updates.
- Observed behavior
- Seeking clarification on the update policy because standard Microsoft 365 Exchange Online support does not cover on-premises server administration.
Before proceeding with any Exchange Server update plans, verify your current Cumulative Update version via the Exchange Management Shell and ensure you have a complete backup of your Active Directory and Exchange databases.
Review the Exchange Support Policy and Consult Official Forums
Understand the Microsoft Exchange N-1 servicing model and direct architectural questions to the specialized Exchange Administration community for accurate deployment advice.
Microsoft 365 Business Exchange Online Support specializes in cloud configurations and does not handle on-premises Exchange Server inquiries. To ensure you receive accurate and safe upgrade instructions for your specific topology, you should consult the official Exchange Server Administration forums.
As a general rule, Microsoft supports the current Cumulative Update (CU) and the immediately preceding one (N-1) with Security Updates. However, since Exchange 2016 CU23 is the final cumulative update for this product, upgrading to CU23 is highly recommended to receive all future security patches.
Verify your current Exchange version. Under the N-1 model, CU22 receives security updates for a limited time after CU23 is released, but eventually, you must upgrade to CU23 (the final CU) to stay protected.
Navigate to the dedicated Microsoft Q&A platform for Exchange Server administration: https://learn.microsoft.com/en-us/answers/topics/46490/office-exchange-server-administration.html
Submit a question detailing your current Windows Server OS, hybrid setup status, and current CU22 build number. The specialized engineering team will guide you on the safest upgrade path.
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Frequently Asked Questions
What is the latest Cumulative Update for Exchange 2016?
Cumulative Update 23 (CU23) is the final cumulative update released for Microsoft Exchange Server 2016. Moving forward, the platform only receives specific Security Updates (SUs).
Will Exchange 2016 CU22 still receive security updates?
Under Microsoft's traditional N-1 model, CU22 received updates temporarily after CU23 was released. However, as CU23 is the final CU, staying on CU22 indefinitely will leave your server unsupported and vulnerable. Upgrading to CU23 is required for long-term security patching.
Can I install Security Updates directly without installing the latest CU first?
Security Updates are specific to the Cumulative Update version. You must download the SU specifically packaged for your current CU. If your CU has fallen out of support, you must first install the latest CU before you can apply the most recent security patches.
Why can't standard Microsoft 365 support help with on-premises Exchange?
Microsoft 365 Business Exchange Online Support teams are specialized in cloud-hosted environments. On-premises server configurations require specialized Active Directory and local infrastructure knowledge, which is handled exclusively by the Exchange Server Administration community.
