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Microsoft Windows 11 localhost HTTP/2 breakage

Service Disruption
First reported
Last updated
Happening score
H score 0
1 unique sources, 1 articles

Summary

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The October Windows 11 updates broke localhost HTTP/2 connections, preventing local services from completing requests and disrupting debugging and authentication workflows. The issue affects Windows 11 systems that installed KB5066835 and also KB5065789 preview builds. Reported fallout includes Visual Studio debugging, SSMS Entra ID authentication, and Duo Desktop. The main workaround described is to uninstall the updates and restart Windows.

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Timeline

  1. 17.10.2025 01:25 2 articles · 7mo ago

    Windows 11 update breakage disrupts localhost HTTP/2 connections

    Initial Disclosure

    Microsoft's October Windows 11 update set is reported to have broken localhost HTTP/2 connectivity on systems that installed KB5066835 and the September KB5065789 preview update, causing requests to 127.0.0.1 to fail with ERR_CONNECTION_RESET or ERR_HTTP2_PROTOCOL_ERROR and disrupting Visual Studio debugging, SSMS Entra ID authentication, and Duo Desktop; suggested workarounds include registry changes, a Microsoft Defender intelligence update, or uninstalling KB5066835 and KB5065789 and restarting Windows.

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