Windows Server 2022 must prevent PKU2U authentication using online identities.

Severity
Group ID
Group Title
Version
Rule ID
Date
STIG Version
mediumV-254472SRG-OS-000480-GPOS-00227WN22-SO-000280SV-254472r991589_rule2025-02-252
Description
PKU2U is a peer-to-peer authentication protocol. This setting prevents online identities from authenticating to domain-joined systems. Authentication will be centrally managed with Windows user accounts.
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\pku2u\ Value Name: AllowOnlineID 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 PKU2U authentication requests to this computer to use online identities to "Disabled".