Cumulative Update 23 for Exchange Server 2016

Microsoft released Cumulative Update 23 for Exchange Server 2016 (KB5011155) on April 20, 2022. Also known as Exchange Server 2016 CU23. This Cumulative Update includes fixes for nonsecurity issues and all previously released fixes for security and nonsecurity issues. These fixes will also be included in later Cumulative Updates for Exchange Server 2016.

How to update Exchange Server 2016 to CU23?

It’s recommended to update the Exchange Server in the lab environment before updating it in the production environment.

1. Download Cumulative Update CU23 for Exchange Server 2016 (KB5011155)
2. Update to Microsoft .NET Framework 4.8
3. Install Exchange Cumulative Update

Cumulative Update CU23 for Exchange Server 2016 is released as version 15.01.2507.006. Which version are you running now? Read more on how to find your Exchange version build number.

New features in Cumulative Update 23

• To prevent misuse of UNC paths by attackers, parameters that take UNC paths as inputs will no longer be usable in Exchange Server PowerShell cmdlets or the Exchange Admin Center. For more information, see the following Knowledge Base article:
  
  5014278 Changes in Exchange Server PowerShell cmdlets and Exchange Admin Center for UNC path inputs

Known issues in Cumulative Update 23

• The MSExchangeServiceHost service crashes repeatedly and Event ID 4999 is logged in the Windows Application event log. For more information, see Exchange Service Host service fails after installing March 2022 security update.

• The Get-MailboxDatabaseCopyStatus cmdlet from an Exchange Server 2013 server fails against databases on Exchange Server 2019 and 2016 servers and returns Error 0xe0434352 from RpccGetCopyStatusEx4.
  
  Workaround: Run Get-MailboxDatabaseCopyStatus from an Exchange Server 2019 or 2016 server.

• Checking the Exchange Server 2019 or 2016 database status from the Exchange admin center (EAC) might fail and return an “HTTP 500” or “Your request couldn’t be completed. Please try again in a few minutes” error message.
  
  Workaround: Make sure that the admin mailbox is on an Exchange Server 2019 or 2016 server. If the admin account has no mailbox, make sure that all arbitration mailboxes (especially the “SystemMailbox{bb558c35-97f1-4cb9-8ff7-d53741dc928c}”) are on an Exchange Server 2019 or 2016 server.

• The UM Voicemail greetings function stops working and returns error “0xe0434352.”

• The Get-EmailAddressPolicy cmdlet fails and returns “Microsoft.Exchange.Diagnostics.BlockedDeserializeTypeException.”

• “Cannot Send Mail – Your mailbox is full” error when you use iPhone mail to send very large attachments. For more information, see KB 5004622.

Issues fixed in Cumulative Update 23

This Cumulative Update fixes the issues that are described in the following Microsoft Knowledge Base articles:

• 5012757 “Migration user… can’t be found” error when using Start-MigrationUser after batch migration fails
• 5012760 You can’t access OWA or ECP after installing the July 2021 security update
• 5012761 External attendees see “Send the Response Now” although no response was requested in Exchange Server
• 5012765 Email stuck in queue starting from “2022/1/1 00:01:00 UTC+0” on all Exchange on-premises servers
• 5012768 Start-MigrationUser and Stop-MigrationUser are unavailable for on-premises Exchange Server 2019 and 2016
• 5012774 Can’t change default path for Trace log data in Exchange Server 2019 and 2016
• 5012779 Invalid new auth certificate for servers that are not on UTC time zone
• 5012780 Disable-Mailbox does not remove LegacyExchangeDN attribute from on-premises Exchange 2019
• 5012781 Exchange Server 2019 and 2016 DLP doesn’t detect Chinese resident ID card numbers
• 5012782 MS ExchangeDiagnostic Service causes errors during service startup and initialization in Microsoft Exchange 2019
• 5012783 Can’t restore data of a mailbox when LegacyDN is empty in the database
• 5012784 Exchange 2016 CU21 and Exchange 2019 CU10 cannot save “Custom Attributes” changes in EAC
• 5012786 Forwarded meeting appointments are blocked or considered spam
• 5012787 Download domains created per CVE-2021-1730 don’t support ADFS authentication in OWA
• 5012789 Can’t use Copy Search Results after eDiscovery & Hold search
• 5012791 MailboxAuditLog doesn’t work in localized (non-English) environments
• 5012829 Group metrics generation fails in multidomain environment

File hash information

• File name: ExchangeServer2016-x64-cu23.iso
• SHA256 hash: B25A265D8A90C2E069B051C5E6839767143E5512B9224F7E5B8BB875A0CACE41