Vulnerability Discussion

The registry is integral to the function, security, and stability of the Windows system. Changing the system's registry permissions allows the possibility of unauthorized and anonymous modification to the operating system.

Check

Review the registry permissions for the keys of the HKEY_LOCAL_MACHINE hive noted below.

If any non-privileged groups such as Everyone, Users, or Authenticated Users have greater than Read permission, this is a finding.

If permissions are not as restrictive as the default permissions listed below, this is a finding:

Run "Regedit".

Right-click on the registry areas noted below.

Select "Permissions" and the "Advanced" button.

HKEY_LOCAL_MACHINE\SECURITY

Type - "Allow" for all
Inherited from - "None" for all
Principal - Access - Applies to
SYSTEM - Full Control - This key and subkeys
Administrators - Special - This key and subkeys

HKEY_LOCAL_MACHINE\SOFTWARE

Type - "Allow" for all
Inherited from - "None" for all
Principal - Access - Applies to
Users - Read - This key and subkeys
Administrators - Full Control - This key and subkeys
SYSTEM - Full Control - This key and subkeys
CREATOR OWNER - Full Control - This key and subkeys
ALL APPLICATION PACKAGES - Read - This key and subkeys

HKEY_LOCAL_MACHINE\SYSTEM

Type - "Allow" for all
Inherited from - "None" for all
Principal - Access - Applies to
Users - Read - This key and subkeys
Administrators - Full Control - This key and subkeys
SYSTEM - Full Control - This key and subkeys
CREATOR OWNER - Full Control - Subkeys only
ALL APPLICATION PACKAGES - Read - This key and subkeys
Server Operators – Read – This Key and subkeys (Domain controllers only)

Other examples under the noted keys may also be sampled. There may be some instances where non-privileged groups have greater than Read permission.

Microsoft has given Read permission to the SOFTWARE and SYSTEM registry keys in Windows Server 2019 to the following SID, this is currently not a finding.
S-1-15-3-1024-1065365936-1281604716-3511738428-1654721687-432734479-3232135806-4053264122-3456934681

If the defaults have not been changed, these are not a finding.

Fix

Maintain the default permissions for the HKEY_LOCAL_MACHINE registry hive.

The default permissions of the higher-level keys are noted below.

HKEY_LOCAL_MACHINE\SECURITY

Type - "Allow" for all
Inherited from - "None" for all
Principal - Access - Applies to
SYSTEM - Full Control - This key and subkeys
Administrators - Special - This key and subkeys

HKEY_LOCAL_MACHINE\SOFTWARE

Type - "Allow" for all
Inherited from - "None" for all
Principal - Access - Applies to
Users - Read - This key and subkeys
Administrators - Full Control - This key and subkeys
SYSTEM - Full Control - This key and subkeys
CREATOR OWNER - Full Control - This key and subkeys
ALL APPLICATION PACKAGES - Read - This key and subkeys

HKEY_LOCAL_MACHINE\SYSTEM

Type - "Allow" for all
Inherited from - "None" for all
Principal - Access - Applies to
Users - Read - This key and subkeys
Administrators - Full Control - This key and subkeys
SYSTEM - Full Control - This key and subkeys
CREATOR OWNER - Full Control - Subkeys only
ALL APPLICATION PACKAGES - Read - This key and subkeys
Server Operators – Read – This Key and subkeys (Domain controllers only)

Microsoft has also given Read permission to the SOFTWARE and SYSTEM registry keys in Windows Server 2019 to the following SID.
S-1-15-3-1024-1065365936-1281604716-3511738428-1654721687-432734479-3232135806-4053264122-3456934681