Windows Server 2019 must prevent NTLM from falling back to a Null session.
Severity | Group ID | Group Title | Version | Rule ID | Date | STIG Version |
|---|---|---|---|---|---|---|
| medium | V-205917 | SRG-OS-000480-GPOS-00227 | WN19-SO-000270 | SV-205917r991589_rule | 2025-02-25 | 3 |
| Description |
|---|
| NTLM sessions that are allowed to fall back to Null (unauthenticated) sessions may gain unauthorized access. |
| ℹ️ Check |
|---|
| 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 Type: REG_DWORD Value: 0x00000000 (0) |
| ✔️ 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". |