RDP is not working after windows update on Windows server 2025

Question

RDP is not working after windows update on Windows server 2025

Henk Nijland 20

After installing the latest updates on our Windows 2025 servers a rdp session can not be set up.

In the event log id: 6167 says

afbeelding

I found the following solution in https://windowsreport.com/microsoft-confirms-kerberos-and-ntlm-login-issues-in-windows-11-and-server-2025/

Is it possible to send me the group policy to fix this behavior.

Thank you in advance,

Henk Nijland

system administrator gemeente Zutphen

0 comments

Answer accepted by question author

Jason Nguyen Tran 24,545 Independent Advisor

Hi Henk Nijland,

Microsoft has introduced changes affecting Kerberos and NTLM authentication. The workaround involves configuring a specific Group Policy setting to restore compatibility until a permanent fix is released. You can apply this by opening the Group Policy Management Console and navigating to: Computer Configuration > Administrative Templates > System > KDC (Kerberos Key Distribution Center). There, enable the policy that allows fallback to NTLM when Kerberos tickets fail. This ensures that RDP sessions can be established while maintaining secure authentication.

Alternatively, you can use the registry to apply the same setting if Group Policy is not available. Please note that this should be considered a temporary workaround, and once Microsoft releases the official patch, it is recommended to revert the change to maintain optimal security.

In summary, applying the Group Policy to allow NTLM fallback will resolve the immediate RDP login issue. Please ensure that you monitor Microsoft’s update channel for the permanent fix.

You can try and feel free to let me know if you need further information. If you find this answer helpful, please consider clicking Accept Answer so I know your concern has been resolved.

Jason.

0 comments

2 additional answers

Your answer

Answer 1

Henk Nijland 20

Dear Jason,

I applied the following dword in the registry on both servers.

AllowNtAuthPolicyBypass=1 in Computer\HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Kdc

User's image

But this does not solve the problem. I still get the error message (I rebooted both servers):

User's image Is there something I did wrong?

Greets,

Henk Nijland

0 comments

Answer 2

Henk Nijland 20

Hello Jason,

I don't have this option???: enable the policy that allows fallback to NTLM when Kerberos tickets fail

User's image

Jason Nguyen Tran 24,545 Reputation points Independent Advisor

2026-02-20T01:32:04.2666667+00:00

Hi Henk,

At present, the specific policy setting to allow fallback to NTLM when Kerberos tickets fail is only available in updated Administrative Template files (ADMX/ADML) that ship with newer cumulative updates. If your domain controllers or local Group Policy Editor have not yet been updated with the latest templates, the option will not be visible. In such cases, the supported workaround is to apply the registry equivalent directly. You can create a DWORD value under HKLM\System\CurrentControlSet\Control\Lsa\Kerberos with the appropriate flag to enable NTLM fallback. Microsoft has documented this registry path in recent support notes related to Kerberos/NTLM hardening.

Alternatively, you can download the latest ADMX templates from Microsoft’s official site and copy them into your PolicyDefinitions folder. Once updated, the new Kerberos/NTLM settings will appear in Group Policy Editor under Computer Configuration > Administrative Templates > System > KDC.