October Windows updates can disrupt 802.1X authentication

Neowin reports that Microsoft acknowledged a change in the October 13, 2026, updates—KB5127648 for Windows 11 and KB5126646 for Server 2025—that can disrupt Wi-Fi, Ethernet and VPN connections relying on MS-CHAPv2 authentication. When Credential Guard is disabled, NTLMv1 enforcement now starts by default even without a configured BlockNtlmv1SSO value. Microsoft says setting that value to 0 temporarily restores Audit mode but reduces protection.