Overview

The article describes the disabling of the UDP protocol when using Windows Remote Desktop.  An upgrade of the Remote Desktop version 1.2.6186 that fixed a remote exploit vulnerability CVE-2025-27487. System Five on Cloud users may now experience no connection after entering password credentials.  


UPDATE 2025-05-02:  You can now upgrade to the next version 1.2.6188, and avoid having to disable UDP.  This can be done from the Microsoft download link and choose that version or greater. Note that at the time of this article, the text on the webpage still showed 1.2.6186, but clicking the download link downloaded 1.2.6188.


Disable UDP for System Five on Cloud

Disabling UDP will need to be performed on all workstations impacted.  Disabling UDP allows the connection to be established, but may have performance issues on some networks.  You may want to consider downgrading if you have performance issues on your network.


Back up the Windows Registry

When making changes to your registry, best practice is to create a backup in case you need to restore.

  1. Search the Start menu for regedit.exe and select to run. You may need to provide administrator access when prompted.
  2. Locate and click HKEY_LOCAL_MACHINE 
  3. Right click and choose to Export.
  4. Select the save location and enter a file name, then click Save.


To Disable UDP apply for Remote Desktop

Downloading and applying the Remote-Desktop-Disable-UDP registry file will make the following changes to your registry.

[HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows NT\Terminal Services\Client]

"fClientDisableUDP"=dword:00000001

  1. Search the Start menu for regedit.exe and select to run. Provide administrator access when prompted.
  2. Download Remote-Desktop-Disable-UDP.reg
  3. Double-click to merge the registry file.  
  4. You will be prompted if you want to Run the file.
  5. You will also be prompted if you want to continue, and will need to answer Yes.
  6. Proceed to sign into System Five on Cloud.


To Re-enabled UDP for Remote Desktop

If you have performance issues and wish to re-enable UDP.  Download and applying the Remote-Desktop-Enable-UDP registry file will make the following changes to your registry.  You may want to consider downgrading if you have performance issues on your network.


[HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows NT\Terminal Services\Client]

"fClientDisableUDP"=dword:00000000

  1. Search the Start menu for regedit.exe and select to run. Provide administrator access when prompted.
  2. Download  Remote-Desktop-Enable-UDP.reg.
  3. Double-click to merge the registry file.  
  4. You will also be prompted if you want to continue, and will need to answer Yes.