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 ...

Microsoft’s latest Windows 11 patch tripped over its own shoelaces and knocked out localhost, leaving devs unable to reach web apps running on their own machines. The October cumulative update ...

On October 14, 2025, Microsoft released the Windows 11 cumulative update KB5066835. It was intended to deliver security fixes and stability improvements, but instead introduced a serious problem. The ...

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" ...

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 ...

Windows updates usually bring security enhancements, bug fixes and new features. Sometimes, though, these updates can also break parts of the operating system. Unfortunately, some updates for ...