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


Overview

Finding ID Version Rule ID IA Controls Severity
V-220934 WN10-SO-000180 SV-220934r569187_rule Medium
Description
NTLM sessions that are allowed to fall back to Null (unauthenticated) sessions may gain unauthorized access.
STIG Date
Windows 10 Security Technical Implementation Guide 2021-08-18

Details

Check Text ( C-22649r555287_chk )
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 (F-22638r555288_fix)
Configure the policy value for Computer Configuration >> Windows Settings >> Security Settings >> Local Policies >> Security Options >> "Network security: Allow LocalSystem NULL session fallback" to "Disabled".