I'm trying to RDP into one of my servers, which as Network Level Authentication Enabled as well as NTLMv2 being forced. This worked fine until the server had to reboot for updates. Now, I cannot RDP into my server anymore. I get this error trying to connect via RDP:
An authentication error has occurred - The function requested is not supported
This translates to: An authentication error has occurred. The function requested is not supported
I tried several things I found by googling, for example adding extra SecurityPackages values to the registry as described here: http://funeasytech.com/rdp-connection-error-of-the-requested-security-package-does-not-exist/ but that didn't work. Neither did changing the Group Policy on the client solve my issue, as described here: https://stackoverflow.com/questions/17371311/the-function-requested-is-not-supported-exception-when-using-smtpclient-in-azu
The problem is that I don't have physical access to this box, only via RDP. The server is running Windows Server 2012 R2 Standard, the client is running Windows 10 Pro.
How can I regain access to my server?
1:
I had the same issue. I found the issue has to do with a Windows Update patch that was pushed out to my work station in last nights Windows Updates. There was a critical CVE (CVE-2018-0886) for RDP which required a patch to fix.
If your workstation is patched, but your server isn't, your workstation will fail to connect.
Quoting from the following blog website with information about the issue, you've got three options:
I didn't have alternative access to the server(remote access only), so I had to chose Option 2 so I could go do the updates on the server.
I opened the start menu on my work station, searched for "group policy", clicked Edit Group Policy. Then following Microsoft spec, Go to "Computer Configuration -> Administrative Templates -> System -> Credentials Delegation", then :
See Windows RDP: ‘An authentication error has occurred’
This is happening after you have a applied a windows security update it was this security update. It also tells you how to change your GPOs accordingly.
Don’t Simply Uninstall Windows updates KB41037272. and or KB4103718 – just because something works does not mean that’s what you should do!
I had the same issue with a remote VM, with only RDP access. This worked for me...
If your target server is Windows Server 2016, the first package from this list (2018-05 Cumulative Update for Windows Server 2016 for x64-based Systems (KB4103723)) worked for me:
As already mentioned, this is the recommended way and does not require any other changes on source machines.
For Windows Server 2012 R2 the package 2018-05 Security Only Quality Update for Windows Server 2012 R2 for x64-based Systems (KB4103715) from here solved the issue.