Windows Update KB5066835 Causes IIS Connection Failures
Windows Update KB5066835 Causes IIS Connection Failures, Microsoft Confirms
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Windows Update KB5066835 Causes IIS Connection Failures, Microsoft Confirms
Microsoft acknowledges widespread server connectivity issues affecting Windows 11 and Windows Server 2025 users
On October 16, 2024, Microsoft confirmed that recent Windows 11 updates are causing significant problems with server-side applications that rely on HTTP.sys, resulting in connection failures to Internet Information Services (IIS) web servers.
The Problem
Users who installed patches released after September 29, 2024, are experiencing incoming connection issues with server-side applications that depend on HTTP.sys. The problems manifest in several ways:
- IIS websites failing to load completely
- Connection reset errors (ERR_CONNECTION_RESET) appearing in browsers
- Websites hosted on “http://localhost/” becoming inaccessible
The issue doesn’t affect all systems uniformly. Whether a particular device experiences the problem depends on multiple factors, including internet connection status, the timing of recent update installations, and when the device was last restarted.
Affected Systems
Microsoft has identified the following platforms as vulnerable to this issue:
- Windows 11 version 25H2
- Windows 11 version 24H2
- Windows Server 2025
This is particularly concerning for organizations running web servers and development environments on these platforms, as the connectivity failures can disrupt business operations and development workflows.
Recommended Solutions
Microsoft has provided a troubleshooting procedure for affected users:
- Open Windows Update settings
- Click “Check for updates” and allow any available updates to install
- Restart the device (even if no new updates are installed, a restart is mandatory)
Microsoft’s Response
Microsoft is implementing a temporary fix through its Known Issue Rollback (KIR) system. For consumer devices not managed by organizations, the solution should apply automatically. However, enterprise environments—such as workplace or school-managed devices—will need administrators to apply a specific Group Policy provided by Microsoft to resolve the issue.
The company has not yet announced when a permanent fix will be released through standard Windows Update channels.
Impact on Users
This issue is particularly disruptive for:
- Web developers testing applications locally
- Small businesses running IIS-based websites
- Organizations using Windows Server 2025 for web hosting
- IT professionals managing server infrastructure
Users experiencing these problems should follow Microsoft’s recommended troubleshooting steps immediately to restore normal functionality. Organizations with multiple affected systems should prioritize applying the Group Policy fix to minimize service disruptions.
As this is an ongoing situation, users are advised to monitor Microsoft’s official support channels for updates and permanent solutions to this HTTP.sys connectivity problem.
