After installing the usual client security updates on my Microsoft Windows Client Virtual Machine I was suddenly no longer able to connect to the customers Windows Servers. First, I had suspected a server security update shutting out my VM (which would have been understandable). But further investigation pointed to a client issue. Especially the specific error message (if you read it *ahem*) helps:

An authentication error has occurred.
The function requested is not supported.
Remote computer:
This could be due to CredSSP encryption oracle remediation.
For more information, see https://go.microsoft.com/fwlink/?linkid=866660


So if you read upon that link, it appears that a Windows Update on my client installed and activated the CredSSP fix for CVE-2018-0886 in "Force Updated Clients" mode which hindered me to connect to the unpached (*ahem*) servers.

In order to "fix" my access problem, I had to modify the behaviour of the client fix via this command line:
reg add "HKLM\Software\Microsoft\Windows\CurrentVersion\Policies\System\CredSSP\Parameters" /f /v AllowEncryptionOracle /t REG_DWORD /d 2


/via Remote desktop connection error after updating Windows 2018/05/08 - CredSSP updates for CVE-2018-0886 - Super User

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This is the Blog of Martin Leyrer, currently employed as IT-Specialist at IBM Austria - IBM Software Group, IBM Collaboration Solutions.

The postings on this site are my own and do not represent the positions, strategies or opinions of any former, current or future employer of mine.