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V-253458

CAT II (Medium)

NTLM must be prevented from falling back to a Null session.

Rule ID

SV-253458r991589_rule

STIG

Microsoft Windows 11 Security Technical Implementation Guide

Version

V2R7

CCIs

CCI-000366

Discussion

NTLM sessions that are allowed to fall back to Null (unauthenticated) sessions may gain unauthorized access.

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\Control\LSA\MSV1_0\

Value Name: allownullsessionfallback

Value Type: REG_DWORD
Value: 0

Fix Text

Configure the policy value for Computer Configuration >> Windows Settings >> Security Settings >> Local Policies >> Security Options >> "Network security: Allow LocalSystem NULL session fallback" to "Disabled".