Critical Fix: Microsoft Rushes Patch for Windows 11 Localhost Bug

Last week, Microsoft’s latest Windows 11 cumulative update inadvertently broke localhost authentication, hindering developers from debugging via localhost or 127.0.0[.]1. The issue affected Windows 11 versions 24H2 and 25H2, and the emergency update released to resolve the local address access problem is being distributed automatically through Windows Update.

Microsoft notes that the update may take up to 48 hours to reach all affected systems, but developers can speed the process by restarting their PCs while connected to the internet to force immediate patch delivery. If a reboot does not resolve the problem, users can manually edit the system registry to force Windows to use the HTTP/1.1 protocol, via a PowerShell Administrator command that modifies the registry. The bug primarily affects HTTP/2 connections, and the fix essentially rolls back the changes to restore normal localhost connectivity.