Title

The service principal name (SPN) target name validation level must be turned off. (Cat II impact)

Discussion

If a service principle name (SPN) is provided by the client, it is validated against the server's list of SPNs. Implementation may disrupt file and print sharing capabilities.

Check Content

If the following registry value does not exist or is not configured as specified, this is a finding: Registry Hive: HKEY_LOCAL_MACHINE Registry Path: \System\CurrentControlSet\Services\LanmanServer\Parameters\ Value Name: SmbServerNameHardeningLevel Type: REG_DWORD Value: 0

Fix Text

Configure the policy value for Computer Configuration -> Windows Settings -> Security Settings -> Local Policies -> Security Options -> "Microsoft network server: Server SPN target name validation level" to "Off".

Additional Identifiers

Rule ID:

Vulnerability ID: V-21950

Group Title:

Expert Comments

CCIs tied to check.

Controls tied to check. These are derived from the CCIs shown above.