ThioJoe covers a recent Windows Patch Tuesday update that temporarily broke HTTP/2 localhost connections and explains which apps were affected. He details Microsoft’s rollback solution and offers ...

After the recent Windows 11 update KB5066835, many developers found their local web servers — including IIS, IIS Express, and Kestrel — suddenly failing to load. Browsers began throwing ERR_CONNECTION ...

In environments where the cumulative update for Windows 11 released by Microsoft in October 2025 (KB5066835) has been applied, an issue has occurred where localhost is no longer accessible. This has ...

Microsoft has fixed a known issue breaking HTTP/2 localhost (127.0.0.1) connections and IIS websites after installing recent Windows security updates. This bug affects both Windows 11 and Windows ...

Update 10/17/25: Microsoft fixes the bug using a KIR (Known Issue Rollback) update. More information added to end of story. Microsoft's October Windows 11 updates have broken the "localhost" ...

What just happened? Microsoft continues its tradition of making Windows a little more cumbersome with each monthly patch cycle. Following the October update, Windows 11 admins and developers are ...

The problem first surfaced on Microsoft's own support forums and quickly spread to Stack Overflow and Server Fault after the October 2025 cumulative update (KB5066835) landed, which appears to have ...