RDP authentication error due to CredSSP encryption oracle remediation after May 2018 Windows Updates

 

If you are getting an error using RDP to connect to a Windows Server and error say “Remote Desktop Connection: An authentication error has occurred.  The function requested is not supported. This could be due to CredSSP encryption oracle remediation”, this is because you are connected from an unpatched client to a patched server or a patched client to an unpatched server.

To fix this issue, install the May 2018 Windows Updates on both the server and the local PCs.

Microsoft has been patching a vulnerability in RDP/CREDSSP with the patches released this month (May 2018) and previous month or two, and as of the May 8 updates, it requires BOTH the client PCs and the Windows Server to both have the May patches installed.

Below is a link about it but best is to apply the patches….
https://blogs.technet.microsoft.com/yongrhee/2018/05/09/after-may-2018-security-update-rdp-an-authentication-error-occurred-this-could-be-due-to-credssp-encryption-oracle-remediation/

 

UPDATED 5/10/2018 –

Additional links discussing this issue below.  Best approach is just install Windows Updates on both Servers & Client/local PCs  and everything should work.  If you are unable to patch your server immediately, there are some suggested workarounds (registy/GPO modifications, disable NLA (not recommended due to lower security), etc.  We strongly recommend you apply the May 2018 Windows Updates.

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

https://community.spiceworks.com/topic/2120195-get-patching-cve-2018-0886-credssp-flaw-in-rdp-affects-all-versions-of-windows?page=3