After May 2018 security update: RDP "An authentication error occurred" "This could be due to CredSSP encryption oracle remediation".

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[Client] i.e. On a Windows 10

When an IT Admin was trying to RDP to a Windows Server, they were getting the following error:

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May 2018 'security update' is installed.

[CAUSE]

Starting in the May 2018 Security update we are enforcing the March 2018 CVE-2018-0886.

CredSSP updates for CVE-2018-0886

https://support.microsoft.com/en-us/help/4093492/credssp-updates-for-cve-2018-0866-march-13-2018

My colleagues Paul and Graeme go more in-depth here:

CredSSP, RDP and Raven
https://blogs.technet.microsoft.com/askpfeplat/2018/05/07/credssp-rdp-and-raven/

[Server where RDP to is failing]

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May 2018 'security update' is not installed. Matter of fact, this hasn't been patched since May of 2017.

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Deleted the gpo in the registry

Restarted WU service

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The WSUS/SCCM admin needs to check why some of the Servers are not getting the security updates.

Thanks,

Yong [Somewhere in NorCal for the week]