Exchange 2013 CU6 – The third Cumulative Update in a row that is facing issues :(

On August 26 Microsoft released Exchange 2013 CU6, the sixth Cumulative Update since the new servicing model of Exchange 2013, exactly after 90 days which fits in the quarterly cadence.

Besides the Cumulative Update itself a new CU6 UM Language Pack is available as well. You can find more information in the Microsoft Knowledgebase article KB2961810 and the Release Notes.

As discussed earlier (actually it was announced at last MEC in Austin) CU6 contains an improvement in the supported number of Public Folder (now 100,000 which equals to the number of supported Public Folders in Office 365). Also a hotfix for a nasty issue that occurred in CU4 (=SP1) and CU5 in combination with the Hybrid Configuration Wizard (kb2988229) is included in this Cumulative Update.

Unfortunately this is the third Cumulative Update in a row that is facing issues. Soon after its release customers found two issues with Exchange 2013 CU6:

Both issues were quickly identified by Microsoft and a fix is already available.

Please have a look at the support lifecycle of Cumulative Updates and Service Packs. A Service Pack is supported by Microsoft 12 months after the release of the next Service Pack so when you are running Exchange 2013 SP1 you are fine.

A Cumulative Update on the other hand is supported 90 days after the release of the next Cumulative Update. So, CU3 is supported 90 days after the release of CU5. This means that only the current CU and the previous CU are supported, older CU’s are no longer supported.

This was visible with the HCW issue in CU5. A hotfix was released for CU5 and CU4 (=SP1) but not for CU3 anymore. At the same time upgrading from CU3 or older to CU6 is officially not supported by Microsoft. If you are running CU3 or older we strongly recommend you upgrade to a newer Cumulative Update.

More information regarding servicing Exchange 2013 can be found on When Microsoft released Exchange 2013 CU6 Update Rollups for Exchange 2010 and Exchange 2007 were released as well:

As always, before you implement one of these in your production environment iRangers urge you to test it thoroughly in a test environment, or contact us to discuss the potential impact ;)!

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