Microsoft’s recent updates for Windows 11 have inadvertently disrupted the functionality of the “localhost” feature, which is crucial for developers and applications that rely on local connections. The localhost, accessible via the IP address 127.0.0.1, serves as a vital testing ground for web applications and debugging processes.
Impact of Recent Updates
Following the installation of the October update, designated as KB5066835, along with September’s KB5065789 preview update, users have reported significant connectivity issues. Applications that typically establish HTTP connections to localhost are now encountering errors such as “ERRCONNECTIONRESET” and “ERRHTTP2PROTOCOL_ERROR.” This disruption has been widely discussed across various platforms, including Microsoft forums, Stack Exchange, and Reddit, where users express their frustrations over the inability to connect to 127.0.0.1.
The bug has particularly affected popular applications, including Visual Studio for debugging, SSMS Entra ID authentication, and the Duo Desktop app, which is essential for verifying device security and requires local web server connections. A support bulletin from Duo highlights the consequences of this issue, stating, “After performing Windows Updates for Windows 11 24H2 and 25H2, you may experience an issue where the Duo Prompt is unable to reach Duo Desktop.” This situation can hinder successful authentication processes, especially in environments utilizing Trusted Endpoints and various Duo policies.
Potential Solutions
In response to these challenges, some users have found potential workarounds. One suggested method involves modifying specific Registry entries to disable the HTTP/2 protocol. However, this fix has not been independently verified by BleepingComputer:
[HKEYLOCALMACHINESystemCurrentControlSetServicesHTTPParameters]
"EnableHttp2Tls"=dword:00000000
"EnableHttp2Cleartext"=dword:00000000
Another proposed solution is to install the latest Microsoft Defender intelligence update, although reports on its effectiveness remain mixed. For those seeking a more definitive resolution, the most reliable approach appears to be uninstalling the problematic updates. Users can execute the following commands to remove the updates:
wusa /uninstall /kb:5066835
wusa /uninstall /kb:5065789
After performing these uninstalls and restarting their systems, users have found that the loopback interface is restored, allowing HTTP/2 connections to function correctly once again.
BleepingComputer has reached out to Microsoft for further clarification on this issue and will provide updates as they become available.
In the meantime, the ongoing situation underscores the importance of careful update management and the potential ripple effects that seemingly routine patches can have on critical development tools and workflows.
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