Microsoft's latest updates for Windows 11 have disrupted localhost functionality, particularly impacting applications that utilize HTTP/2 connections to the 127.0.0.1 address. This issue has raised concerns among developers who rely on localhost for testing and running local services.
Issues with Localhost Connections
Following the October Patch Tuesday and September preview updates, many applications can no longer establish HTTP connections to 127.0.0.1. Users are encountering errors such as "ERR_CONNECTION_RESET" and "ERR_HTTP2_PROTOCOL_ERROR." Localhost, or the local machine address, is crucial for software development and diagnostics, affecting tools like Visual Studio, SSMS, and services using Entra ID for authentication. The Duo Desktop app is also facing issues, resulting in authentication problems or limited feature functionality.
Workarounds and Solutions
In response to these issues, some users have found success by disabling HTTP/2 via specific registry edits:
- [HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\HTTP\Parameters] "EnableHttp2Tls"=dword:00000000 "EnableHttp2Cleartext"=dword:00000000
However, this solution requires careful handling, as it has not been independently verified by all users. An alternative and more reliable resolution is uninstalling the problematic Windows 11 updates—KB5066835 and September's KB5065789 preview update. This can be done by executing the following commands:
- wusa /uninstall /kb:5066835
- wusa /uninstall /kb:5065789
After removal and a system restart, HTTP/2 connections via the loopback address should resume functioning as expected. Meanwhile, Microsoft has been contacted for further comments on the issue and possible long-term fixes.
