Microsoft Releases April 2024 Hotfix Updates for Exchange Server 2016 and 2019

Microsoft has released optional April 2024 hotfix updates for Exchange Server 2016 and 2019, addressing issues from the March 2024 Security Update and introducing support for Elliptic Curve Cryptography (ECC) certificates and Hybrid Modern Authentication for Outlook Web App (OWA) and Exchange Control Panel (ECP).

The April 2024 hotfix update (HU) includes all the updates from the March 2024 Security Update (SU) and is available for specific builds of Exchange Server. It resolves several non-security issues and can be installed directly, even if the March 2024 SU has not been applied. The new features of ECC certificate support and Hybrid Modern Authentication for OWA/ECP will be included in future updates as well.

The hotfixes address multiple known issues that arose after the installation of the March 2024 security updates, such as problems with download domains, inline images, attachment downloads, document previews, search errors, probe failures, permission editing, unread envelope icons, add-in malfunctions, and calendar printing in OWA. "The April 2024 HU includes the same security updates as the March 2024 security update (SU), while addressing the known issues with the March 2024 SU," stated the Exchange Team.

ECC certificates are now supported in Exchange Server 2016 and 2019, with a limitation that ECC is not available in Active Directory Federation Services (AD FS) environments. The April hotfix for Exchange 2019 CU14 also adds support for Hybrid Modern Authentication (HMA) for OWA and ECP.

Why this matters: The release of these hotfixes comes amid criticism over Microsoft's handling of security on Exchange, following a breach by Russian espionage operatives. The updates aim to improve the security and functionality of Exchange Server environments, addressing issues caused by previous security updates and introducing new features to enhance authentication and certificate support.

Microsoft has announced the end of mainstream support for Exchange Server 2019, while Exchange Server 2016 is under extended support until October 2025. The company is providing guidance and information to help global admins decide on the migration path to Exchange Online. The hotfixes are optional and cumulative, meaning that users who skipped the March update will also receive the security fixes in the April hotfix. Microsoft is still working on a fix for an issue where calendar printing in OWA might not work unless the CTRL+P keyboard shortcut is used.

Key Takeaways

• Microsoft released optional April 2024 hotfix updates for Exchange Server 2016 and 2019.
• The updates address issues from the March 2024 Security Update and add ECC certificate support.
• The hotfixes resolve various non-security issues, including problems with downloads, search, and calendars.
• Exchange Server 2019 has reached end of mainstream support, while 2016 is in extended support.
• The updates aim to improve security and functionality, addressing issues caused by previous updates.