Remote Desktop Connection Authentication error

Article
2018-05-09

Question

_{Wednesday, May 9, 2018 5:32 PM}

After Windows Update, yesterday, I could not connect to a remote host via RDP any more (and I could connect útil before updates)

I receive this erorr:

An Authentication error has occurred

The function request is not supported

Remote cometer: x.x.x.x (ip Address)

This could be due to CredSSP encryption Oracle remediation.

For more information see https://go.microsoft.com7fwlink/?linkid=866660

I tried to change registry Key AllowEncryptionOracle

in HKLM\Software\Microsoft\Windows\CurrentVersion\Policies\System\CredSSP\Parameters

But nothig change.

In my Windows 10 I have the error log:

Log Name: System

Source: LsaSrv

Date: 9/5/2018 10:29:54

Event ID: 6041

Task Category: None

Level: Error

Keywords: Classic

User: N/A

Computer: JuanCC-NB

Description:

A CredSSP authentication to TERMSRV/X.X.X.X (ip Address) failed to negotiate a common protocol version. The remote host offered version 3 which is not permitted by Encryption Oracle Remediation.

See https://go.microsoft.com/fwlink/?linkid=866660 for more information.

Event Xml:

<Channel>System</Channel>

<Computer>JuanCC-NB</Computer>

</System>

<Data>TERMSRV/172.16.4.143</Data>

</EventData>

</Event>

What should I change in remote Machine?

I have problems accessing to a Windows 10 and to Windows Server 2012 R2

Thanks in advanced

Best Regards

JuanCC Technology Specialist

All replies (7)

_{Sunday, May 13, 2018 7:13 AM ✅Answered}

Hi JuanCC,

i also faced the same issue, you need to check this

https://blogs.technet.microsoft.com/mckittrick/unable-to-rdp-to-virtual-machine-credssp-encryption-oracle-remediation/

_{Thursday, May 10, 2018 4:01 AM | 1 vote}

Hi,

Have a look in your Documents folder, there is a Default.rdp hidden file (enable Hidden Items on the View toolbar in File Explore if needed to see it) Delete that file and new will be created on next connection, try that.

Also check this article for assistance. Try install Domain Controller Certificate on the domain controller for the user’s credential verification. No need to disable NLA.

An Authentication error has occurred. The Function requested is not supported.

https://itluke.online/2018/03/29/solved-authentication-error-function-not-supported/

Please Note: Since the websites are not hosted by Microsoft, the links may change without notice. Microsoft does not guarantee the accuracy of this information.

Best Regards,

Tao

Please remember to mark the replies as answers if they help. If you have feedback for TechNet Subscriber Support, contact [email protected].

_{Sunday, May 13, 2018 1:53 PM}

JuanCC, Did you follow the more information link ? https://go.microsoft.com/fwlink/?linkid=866660

_{Monday, May 14, 2018 4:34 PM | 1 vote}

You need to make sure both your workstations and servers are patched with the March CredSSP patch. On May Patch Tuesday, Microsoft released a patch that basically enforces the March patch, so if your workstation got the May patch but you're trying to connect to servers that haven't received the March patch, you'll get this error.

As a workaround, you can push a Group Policy out or edit a registry key locally, but neither one of those is considered a long-term permanent solution.

You can read - How to Fix Authentication Error Function Not Supported CredSSP Error RDP for more information on the Group Policy and registry key.

For the Group Policy, you'll need the ADMX files from a patched server. In the article above, there's a link to those files from a patched Windows 2012 R2 server which should work.

Policy path: Computer Configuration -> Administrative Templates -> System -> Credentials Delegation Setting name: Encryption Oracle Remediation

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System\CredSSP\Parameters]
"AllowEncryptionOracle"=dword:00000002

_{Tuesday, May 22, 2018 12:49 AM}

RBRussell has it right but likely meant to say

"You need to make sure both your workstations and servers are patched with the May CredSSP patch"

The May 10th Updates changed the default value for Encryption Oracle Remediation from Vulnerable to Mitigated. Patched clients communicating with unpatched servers results in a blocked configuration.
See the interop matrix @ the bottom of KB 4093492 and focus on that and other client / server configurations that result in blocked configurations.

_{Thursday, May 24, 2018 9:36 AM}

sorted my problem, many thanks

_{Wednesday, May 30, 2018 3:22 AM | 9 votes}

use this link:

https://gallery.technet.microsoft.com/Remote-desktop-authenticati-a9f4b9f8

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Remote Desktop Connection Authentication error

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