Application not working after Windows 11 October 2025 update

Users are finding that their applications are no longer able to complete HTTP connections to the localhost (127.0.0.1) IP address after October Windows 11 update.  Developers commonly use localhost to test websites or debug applications. Some applications need it to connect to a locally running service to perform some action or query. 

Solution 

  1. Check for updates and if Security Intelligence Update for Microsoft Defender Antivirus - KB2267602 (Version 1.439.210.0) is available, install and restart your computer
  2. If that doesn't resolve the issue, uninstall the October KB5066835 update
    1. Open a command prompt  as Admin and run the following command
      • wusa /uninstall /kb:506683​​​​​​​
    2. Restart the computer
INFO: Bleeping computers has an article with more information.

Environment

  • Windows 11
  • MiniTab
  • PaperCut Print Deploy Client
  • DUO Desktop App
  • Applications that use LocalHost

 

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