Mr. Exchange Server Pro Paul Cunningham wrote a guide for updating single servers and dag servers.

http://exchangeserverpro.com/exchange-2013-installing-cumulative-updates/

After applying updates to Exchange 2013 environment. You will sometimes (yes not all the time) that EAC and OWA will break.

Either displaying this page or a blank page.

exchange-2013-500-error

I have found that there is two problems that occur.

First is that BackEnd site looses it’s certificate somehow:

So just go into bindings

And you will see the selection is empty

So just choose the right one and do iisreset

If this doesn’t work it is the famous CanaryData problem.

You will the see this in Application Log with eventid 4:

And the steps to fix it are:

Open adsiedit and go to

CN=Client Access,CN=ORGNAMEHERE,CN=Microsoft Exchange,CN=Services,CN=Configuration,DC=domain,DC=local

From there clear msExchCanaryData0 and if there is 1,2,3 them also

Then recycle MSExchangeECPAppPool and MSExchangeOWAAppPool

500-error-apppools

That’s it!