After the May 2018 update to Windows 10, users who use Remote Desktop function may experience an issue where they get an error while logging in to a remote computer via RDP.
The error will look as follows:
An authentication error has occurred.
The function requested is not supported
Remote computer: [computername]
This could be due to CredSSP encryption oracle remediation.
For more information, see https://go.microsoft.com/fwlink/?linkid=866660
This is due to a recent vulnerability fixed in Windows 10 and Windows 7. After installing the latest update KB4103727 for Windows 10 Version 1709 and KB4103718 for Windows 7, you will start getting this error.
Solutions to RDP Authentication Error Function Requested Is Not Supported
Solution 1: Install updates on the target computer
The recommended solution to this issue is to update the target computer on which you are trying to connect remotely. If the Server has applied the May BigFix ePatching updates and rebooted the server. It should install the required updates.
If necessary, you can go to Microsoft and install all the updates specifically related to CVE-2018-0886.
Specifically, if the target computer is running Windows Server 2016, you should install KB4103723 and if you are using Windows Server 2012 R2, then you should install KB4103725.
A server reboot will be required after installing these updates.
If you do not want to update the computer or it’s not in your access then you can try the other solutions listed below.
Solution 2: Using Group Policy
1. Go to Run –> gpedit.msc to open Group Policy Editor.
2. Go to the following policy path:
Computer Configuration -> Administrative Templates -> System -> Credentials Delegation
3. From the right-hand pane, open Encryption Oracle Remediation.
4. Select Enabled and set the protection level to Vulnerable.
Encryption Oracle Remediation policy
5. Go to command prompt and run the following command:
gpupdate /force
This will apply the group policy immediately and you will be able to use Remote Desktop without restarting the computer.
