Microsoft's October 2026 Windows update switches on a security tightening that can stop some older Wi-Fi, wired network and VPN connections from signing in.

• What changed: Windows 11 (24H2, 25H2 and 26H2) and Windows Server 2025 now restrict credentials derived from the old NTLMv1 method for single sign-on by default.
• Who is affected: only devices where Credential Guard is turned off, and only connections that rely on the older MS-CHAPv2 sign-in method, which is common on older Wi-Fi and VPN setups.
• The risk: staff may suddenly be unable to join the office network or connect remotely after the update installs.
• Not a bug: Microsoft describes this as a planned change, not a known issue, so it will not be reversed.
• What to do: identify anything still using MS-CHAPv2 and move to certificate-based sign-in. A temporary registry setting can allow and log these connections while you do so (see Microsoft's KB5066470).

We recommend testing Wi-Fi and VPN sign-in on a pilot device before rolling the October update out widely. Contact OzComm Network Solutions if you need help checking your setup. Source: Microsoft Windows message centre.