Resetting Default Access Controls on Selected Registry Keys

• Microsoft Windows NT Workstation versions 3.5, 3.51, and 4.0
• Microsoft Windows NT Server versions 3.5, 3.51, and 4.0

IMPORTANT: This article contains information about editing the registry. Before you edit the registry, make sure you understand how to restore it if a problem occurs. For information about how to do this, view the "Restoring the Registry" Help topic in Regedit.exe or the "Restoring a Registry Key" Help topic in Regedt32.exe.

SYMPTOMS

A user with a valid user name and domain name, who also has the right to log on locally to a Windows NT computer, can have the system run a program on the local computer in a heightened security context.

NOTE: The Guest account does not have access to modify the registry. By default, Windows NT domain controllers only permit administrators to log on and therefore are not vulnerable.

CAUSE

When a properly authenticated user logs on locally to a Windows NT computer, that user becomes a member of the "Everyone" group. The default permission on the keys cited below allow members of the "Everyone" group special access, which includes the right to Set Values or Create Subkeys. This allows members of the "Everyone" group to create an entry under the Run and RunOnce keys that contains the name of a program to run when the computer starts. The Uninstall key defines the programs to run when you remove an application.

   HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
   HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\RunOnce
   HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall

RESOLUTION

Resetting the permissions for these three registry subkeys to READ resolves this issue.

WARNING: Using Registry Editor incorrectly can cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that problems resulting from the incorrect use of Registry Editor can be solved. Use Registry Editor at your own risk.

For information about how to edit the registry, view the "Changing Keys And Values" Help topic in Registry Editor (Regedit.exe) or the "Add and Delete Information in the Registry" and "Edit Registry Data" Help topics in Regedt32.exe. Note that you should back up the registry before you edit it.

Perform the following steps to reset the permissions:

1. Run Registry Editor (Regedt32.exe).

2. Perform the following steps on each of the registry keys identified above:

   A. On the Security menu, click Permissions.

   B. Click "Replace Permissions on Existing Subkeys" so that it is

         selected.
   

   C. Click Everyone, change the Type Of Access to Read, and then click OK.

3. Exit Registry Editor.