Yes, a Windows 11 update killed "localhost" support — Microsoft breaks Windows again

Microsoft’s latest Windows 11 update, KB5066835, has broken localhost support and disrupted development workflows across the ...
Bleeping Computer

Microsoft fixes Windows bug breaking localhost HTTP connections

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 ...
GitHub

Issue with Port Binding on Localhost and 127.0.0.1 when Running Multiple WSL Instances

Ensure you have two WSL 2 instances. Start the second WSL instance (using wsl -d <distribution_name>). Attempt to bind any local port on localhost or 127.0.0.1 (for example, by starting a local web ...
Bleeping Computer

Windows 11 updates break localhost (127.0.0.1) HTTP/2 connections

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" ...