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Windows Update KB5127648 Disrupts Wi-Fi and VPN Authentication

First seen 16 Oct 2026, 13:38 UTC • •
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ThreatCluster AI
ThreatCluster •October 16, 2026 at 13:39 UTC
  • •KB5127648 disrupts Wi-Fi and VPN sign-ins for Windows 11 and Server 2025.
  • •The update affects systems using MS-CHAPv2 and NTLMv1 credentials.
  • •A temporary workaround reduces security against legacy authentication.

Microsoft's October 2026 update KB5127648 has caused disruptions in Wi-Fi and VPN sign-ins for Windows 11 and Windows Server 2025. The update affects systems relying on MS-CHAPv2 and NTLMv1-derived credentials, particularly when Credential Guard is disabled. Users may experience issues with WPA2-Enterprise Wi-Fi authentication over 802.1X and PEAP, impacting various wireless chipsets. A temporary workaround is available by restoring Audit mode, but this reduces protection against legacy authentication methods. The issue is confirmed to affect Windows 11 versions 24H2, 25H2, and 26H2, as well as Windows Server 2025. Microsoft has not indicated any related to this update.

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Timeline

2026-10-14
KB5127648 update released
Microsoft released update KB5127648, causing issues with Wi-Fi authentication on affected systems.
Feeds.4Sysops
2026-10-16
Disruption confirmed
Microsoft confirmed that the update disrupts Wi-Fi, Ethernet, and VPN sign-ins for certain Windows versions.
Feeds.4Sysops

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Common questions

Which Windows versions are affected?
The update affects Windows 11 versions 24H2, 25H2, 26H2, and Windows Server 2025.
Is there a workaround for the issue?
Yes, restoring Audit mode can temporarily resolve the sign-in issues, but it reduces security against legacy authentication.
Has this issue been exploited in the wild?
No, there is no indication of active exploitation related to this update.