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How to Install Cumulative Update 23 (CU23) for Exchange Server 2013?


From time to time, Microsoft releases a set of updates, called the Cumulative Updates (CU), for the Exchange Server which provides a few fixes and vital updates. The Cumulative Update 23 (CU23) for Exchange Server 2013 was released on June 18, 2019. This update fixes several issues which are not security issues. To install such updates, it is important to know the version of your Exchange Server, along with the patch level and the requirements needed.

In this article, we are going to discuss the process to install Exchange Cumulative Update, along with the pre-requisites. We’ll also discuss how to safeguard the Exchange Server during this operation. This is needed because updates are not perfect. There could be many fault points that could hinder the installation of the updates. Unfortunately, if something happens during a Cumulative Update installation, it could bring the Exchange Server operations to a halt.

The process to Install Cumulative Update

If you have a Database Availability Group (DAG) where you have a failover and fault-tolerant setup of more than one Exchange Server, you can divert all operations to the secondary server until the primary server is installed. However, it would be best to first install on the secondary server, leave it for a week to ensure that there were no repercussions, and then proceed to install on the primary server after diverting all operations to the secondary server to ensure business continuity.

The Cumulative Update 23 for Exchange Server can be obtained from the following links:

The below process is ideal for both Database Availability Group (DAG) setups and standalone servers.

The first and most important thing to do is take a backup of the server in question before installing any update. This doesn’t need to be in the normal schedule. An ad-hoc backup can be taken. This comes in handy in case there is an issue with the installation. There are many factors that could conflict with the update of the Exchange Server. These can include the following:

  • A conflicting antivirus
  • A third-party application locking some Exchange Server files
  • An issue with the operating system
  • Hardware issues

These could break the installation of the update as well as interrupt the installation. It’s always best to have a backup beforehand as it could save your bacon.


The Cumulative Update 23 requires that the Microsoft .Net Framework 4.7.2 is installed. Since the update uses some components that require Visual C++, you need to install the Visual C++ Redistributable Packages for Visual Studios 2013. This can be downloaded from the link below:

When installing the Cumulative Update, the setup will inform you of any missing prerequisites. It is to be noted that you must have the Cumulative Update 22 installed before proceeding as you cannot just install the Cumulative Update 23 on a Cumulative Update 1.

After the backup is complete and the prerequisites are installed, make sure that any scheduled backups, antivirus scans on the server, or any other procedure are paused or disabled during the installation. This could impact the installation and the performance of the installation.

One could argue that there is a lot of preparation on the matter, but this is necessary as you must always have a fallback in case something goes wrong. Now, you can go ahead and install the Cumulative Update 23.

What if something goes wrong?

During the setup, there could be an issue where the services are stopped and the installation gets stuck. If the installation is interrupted, the Exchange would come to a halt and services do not start. You can try to fix the problem but there would be too many loose ends to resolve the matter.

If you have a physical server, the problem is even worst. You would end up restoring the server from scratch and might end up installing the server and Exchange Server while restoring the Exchange Server databases.

During the installation, the database along with the log files could get corrupted. You would need to quickly install a new server and Exchange Server, which wouldn’t be a problem. The problem is that you cannot just copy and paste the databases and attach them to a new Exchange Server installation, especially if the database or the transaction log files are damaged. The data is not extractable without the original functioning Exchange Server.

The solution here is to install Stellar Repair for Exchange. Using this software, without a functioning Exchange Server, you can open corrupted Exchange Server EDB files –- from any version of Exchange Server. You can browse through the database and granularly export to PST and other file formats. You can export directly from multiple EDB files to a live Exchange database or Office 365 tenant. Stellar Repair for Exchange helps ensure that no data is lost and the services are restored with minimal downtime.