Why does Windows display a “Bad Image” error when using RealVNC applications?

What causes the error message to appear?

When using RealVNC applications you may see an error message referring to a "Bad Image", as shown in the screenshot below:

This is caused by RealVNC's new RestrictedMode blocking the action.

RestrictedMode is a security feature that helps protect RealVNC applications on Windows systems.

When enabled, it ensures that only properly signed Microsoft DLLs can be loaded by the RealVNC application, significantly enhancing security.

Disabling RestrictedMode

If you need to RestrictedMode for any reason, for example for compatibility reasons with a separate application you have installed on your device:

1. Open Registry Editor (regedit.exe) with administrator privileges
2. Navigate to: HKEY_LOCAL_MACHINE\SOFTWARE\Policies\RealVNC\<appName>
3. Create or modify the String value RestrictedMode
4. Set the value to 0 to disable
5. Restart the RealVNC application

For example, to disable RestrictedMode for RealVNC Connect Viewer:

1. Open Registry Editor (regedit.exe) with administrator privileges
2. Navigate to: HKEY_LOCAL_MACHINE\SOFTWARE\Policies\RealVNC\rvncconnect
3. Create or modify the String value RestrictedMode
4. Set the value to 0 to disable
5. Restart the RealVNC application

appName values:

• vncviewer
• vncserver
• rvncconnect
• rvncserver

RestrictedMode values:

• 1 (or missing): RestrictedMode is enabled (default, recommended)
• 0: RestrictedMode is disabled (opt-out)

Recommendations

RealVNC recommend that you:

• keep RestrictedMode enabled unless you have a specific compatibility requirement
• only disable this feature if absolutely necessary and you understand the security implications
• ensure any decision to disable RestrictedMode is approved by your IT security team