When Exchange 2013 was released it heralded a different servicing strategy compared to Exchange 2007 and 2010 Rollup Updates (RU).  Exchange 2013 uses Cumulative Updates (CU) to deliver the servicing updates to customers.  As previously discussed, a CU is a different animal when it comes to the update methodology.  CUs are larger, cannot be uninstalled and are a full product installation.  This was announced by the Exchange team on the EHLO blog.  

Update 11-12-2013:  Updated post to reflect changes announced with Exchange 2013 RTM CU2

Update 23-03-2014: Updated post to add Exchange 2013 SP1 (Which is CU4)

Update 28-5-2014:  Updated post to add Exchange 2013 CU5

Update 17-7-2014: Moved security update information out of table

How Long Is A CU Supported?

The original support statement was to allow for a period of three (3) months after the release date of the next CU.

When Exchange 2013 RTM CU2 was released, an update was announced.  Customers will continue to receive assistance from Microsoft Support for the lifecycle of the Exchange server product - a customer is not required to be at the most current CU to receive assistance.  There are two scenarios to clarify though:

1. If during the course of a support incident it is determined that the solution is available in a published CU (e.g., CU2), the customer will be required to install the update that contains the fix. We will not be building a new fix to run on top of a CU published earlier (e.g., CU1).
2. If during the course of a support incident it is determined that you have discovered a new problem for which we confirm a fix is required, that fix will be published in a future CU that you can then install to correct the problem reported.

See also the note below regarding security updates and servicing. 

Exchange 2013 Release Dates And Security Update Status

The table below is based off the Exchange 2013 release dates TechNet article.  The intent is to show when an Exchange 2013 build was released and the availability of security updates.  Security updates will be available for 3 months after the next CU release date. 

Exchange Product Lifecycle

The Microsoft lifecycle site is available to indicate the release, Mainstream and extended support dates for Exchange 2013.  Please note that the support lifecycle site has now been updated for Exchange 2013 SP1. 

Exchange 2013 SP1 will be required on the 14th of April 2015.

Cheers,

Rhoderick