Method not found: "Microsoft.Exchange.Security.Authentication.Utility.DeleteFbaAuthCookies" after update to CU18 on Exchange 2016

Question

Hello,

first - I've already posted this question here, but was told that this would be better here in Microsoft Learn Q&A.

we updated from CU15 to CU18 recently on our Exchange 2016, which is powered by a Windows Server 2012 R2.

The setup was successful, clients can connect, sync, send and receive emails. But /owa and /ecp don't work. As user, you get an error 500.

As an admin you see the following:

[MissingMethodException: Method not found: "Void Microsoft.Exchange.Security.Authentication.Utility.DeleteFbaAuthCookies(System.Web.HttpRequest, System.Web.HttpResponse)".]  
   Microsoft.Exchange.HttpProxy.FbaModule.RedirectToFbaLogon(HttpApplication httpApplication, LogonReason reason) +0  
   Microsoft.Exchange.HttpProxy.FbaModule.OnEndRequestInternal(HttpApplication httpApplication) +614  
   Microsoft.Exchange.HttpProxy.<>c__DisplayClass20_0.<OnEndRequest>b__0() +1670  
   Microsoft.Exchange.Common.IL.ILUtil.DoTryFilterCatch(Action tryDelegate, Func`2 filterDelegate, Action`1 catchDelegate) +35  
   System.Web.SyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +142  
   System.Web.HttpApplication.ExecuteStepImpl(IExecutionStep step) +75  
   System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +93  

What I've already done:

• Regenerated SharedConfig files with DependentAssemblyGenerator.exe as shown here: https://learn.microsoft.com/en-us/exchange/troubleshoot/client-connectivity/event-1309-code-3005-cannot-access-owa-ecp & here: https://social.technet.microsoft.com/Forums/office/de-DE/9b8da9e7-0d0c-4b48-96e7-41fcc6fc7e45/exchange-2016-nach-installation-cu16-kein-owa-und-ecp
• Already did .\UpdateCas.ps1 in %ExchangeInstallPath%\bin -> worked, but the error still exists
• Then did a .\UpdateConfigFiles.ps1 in the same directory -> also worked, but the error still exists
• Changed the Site Binding settings as mentioned here: https://social.technet.microsoft.com/Forums/ie/en-US/8e685c14-b88d-4f70-8e70-25f8190888a1/owa-ecp-broken-after-cu9-and-10-missingmethodexception?forum=Exch2016SD
• Then did a IISRESET & reboot after everything

I really don't know what to do anymore. Has somebody the same problem and could provide me with a solution? Thanks!

Answer 1

I could fix the problem now.

I installed a new, fresh Exchange 2016 testing server with latest CU18, replaced the SharedWebConfig.config files at the production server and it worked. Do not forget to run "iisreset" in CMD with administrator rights after that.

Thanks for your help. I'll provide the SharedWebConfig.config files here to help someone when finding this topic: https://1drv.ms/u/s!Al93fbfAEFekoUKzB5D-WubeWVFY?e=99JxtJ