Released: 2024 H1 Cumulative Update for Exchange Server
Published Feb 13 2024 10:03 AM 95.7K Views

Today we are announcing the availability of the 2024 H1 Cumulative Update (CU) for Exchange Server 2019 (aka CU14). CU14 includes fixes for customer reported issues, a security change, and all previously released Security Updates (SUs).

A full list of fixes is contained in the KB article for CU14, but we also want to highlight a few changes in this CU.

Extended Protection enabled by default

As announced in August 2023, by default, starting with CU14, Setup enables the Windows Extended Protection (EP) feature on the Exchange server being installed. This will happen when running the GUI version of Setup and when running the command line version of Setup without using either the /DoNotEnableEP or /DoNotEnableEP_FEEWS setup switch to opt out. Please see the EP setup documentation for more information.

While Setup enables EP by default, it does not validate that your organization is ready for or able to use EP. To validate that your organization is ready, please review the following before running Setup:

If your servers are not ready for using EP (for example, they use SSL offloading or there are mismatches between client and server TLS configuration), and you do not opt out of EP enablement during Setup, it is possible that some functionality may break after installing CU14. If that happens, you must either make the configuration changes to fulfill the prerequisites for EP (recommended), or use the EP script to disable EP on this server after Setup has completed (and in the future, use the Setup switch to opt-out of EP on all servers that do not yet meet EP prerequisites).

That said, we originally released Exchange Server EP support in August 2022. If you haven’t enabled EP yet, it is time to take this step and further secure your Exchange server environment. Additional information can be found in the documentation.

To help you decide how to proceed, we are providing the following decision flow:

E2019CU14EP02.jpg

.NET Framework 4.8.1 support on Windows Server 2022

CU14 also introduces support for .NET Framework 4.8.1, which is only for Windows Server 2022 (and it cannot be installed on older versions). The Exchange Server supportability matrix has been updated to reflect this change.

TLS 1.3 support moved to CU15

We previously announced plans to support TLS 1.3 when running on Windows Server 2022 in CU14. We’re still testing and validating TLS 1.3 with Exchange Server and do not want to delay the release of CU14. Support for TLS 1.3 will be released in CU15 later this year.

CVE-2024-21410 information

To address CVE-2024-21410 (also released today) – please allow CU14 Setup to enable Extended Protection (EP) on your Exchange 2019 servers. On all other versions of Exchange that support it, enabling EP addresses this CVE. Please see Configure Windows Extended Protection in Exchange Server.

If you have servers that currently do not meet the prerequisites for EP, please see the following table:

Scenario that does not support EP

Action to take

SSL Offloading for Outlook Anywhere

SSL Offloading for Outlook Anywhere must be disabled. If Extended Protection is enabled via Exchange Server CU14, the installer will take care of disabling SSL Offloading for Outlook Anywhere.

SSL Offloading on Load Balancer

SSL Offloading is not supported. Use SSL bridging instead with the same SSL certificate as on Exchange Server IIS front end.

Public folders hosted on Exchange Server 2013, 2016 CU22 (or older) or 2019 CU11 (or older)

Move all Public folders to currently supported versions, decommission Exchange Server 2013 which is out of support. Check this table for your Public Folder scenario.

Modern Hybrid agent is used to publish Exchange Server to the internet in hybrid scenario

Identify the Exchange Servers which are published via Modern Hybrid agent, by following the steps outlined in this section of documentation.

On these servers, run Exchange Server CU14 setup in unattended mode and use the /DoNotEnableEP_FEEWS switch to not enable Extended Protection on the EWS front end virtual directory. Our recommendation for securing the server published by the modern agent can be found here.

Please note that CVE 2024-21410 also applies to Exchange Server 2016. For Exchange 2016 servers, follow Configure Windows Extended Protection in Exchange Server if Extended Protection is not already enabled in your organization. We have not released an update for Exchange 2016 today.

Release details

The KB article that describes the fixes in this release and product downloads is:

Running /PrepareSchema is not required unless you are upgrading from CU9 or older. Please see Schema Changes. Running /PrepareAD is required.

After installing a CU, always check for and install any available SUs. The Exchange Server Health Checker will also tell you if any additional steps are needed.

Known issues with this release

  • Outlook clients might fail to connect to the server (repeatedly prompts for credentials) after CU14 is installed in environments that use SSL Offloading on load balancer. If you use SSL Offloading on LB, please note that SSL Offloading is not supported with Extended Protection. SSL Bridging is supported instead, with the same SSL certificate as on Exchange Server IIS front end.
  • CU14 /RecoverServer setup might fail with an error. See "Cannot convert null to type" error and Exchange 2019 CU14 RecoverServer fails. Note that this applies only to /RecoverServer setup and not setup that upgrades from earlier CU to CU14.

Support status

With the release of Exchange Server 2019 CU14, CU12 is no longer supported and will not receive any future SUs. Please update your servers to the latest CU to continue receiving SUs. As of this writing, the support status of different Exchange versions is as follows:

Exchange Server

Support status

Action to take

Exchange 2019 CU13 or CU14

Supported

Update to latest SU

Exchange 2019 CU 12 (and earlier)

Unsupported (no future SUs)

Update to latest CU and latest SU

Exchange 2016 CU23

Supported

Update to latest SU

Exchange 2016 CU22 (and earlier)

Unsupported (no future SUs)

Update to CU23 and latest SU

Exchange Server 2019 is now in Extended Support, and as previously announced, we plan to release one more CU for Exchange Server 2019 (2024 H2 CU, aka CU15).

Additional information

Microsoft recommends that all customers test the deployment of an update in a lab environment to determine the proper installation process for their production environment.

For installation best practices, see Upgrade Exchange to the latest Cumulative Update. See also the Exchange Update Wizard for detailed installation steps.

If you plan to install the update in unattended mode from PowerShell or a command prompt, make sure you specify either the full path to Setup.exe, or use a “.” in front of the command when running Setup directly from the folder containing the CU. If you do not do either of these, Setup may indicate that it completed successfully when it did not. Read more here.

Customers in Exchange hybrid deployments and those using Exchange Online Archiving with an on-premises Exchange deployment are required to deploy the latest CU for product support.

For the latest information on Exchange Server announcements please see What's New in Exchange Server and the Exchange Server Release Notes.

Major updates to this blog post:

  • 2/22/2024: Added information about the new PrerequisitesCheckOnly parameter in our ExchangeExtendedProtectionManagement.ps1 script.
  • 2/20/2024: Added a Known Issues section

The Exchange Server team

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‎Feb 22 2024 01:59 PM
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