Windows 11
Microsoft says the Windows 11 update broke localhost connections, but a fix is already rolling out. Wikimedia Commons

Microsoft is preparing an emergency patch after its latest Windows 11 update caused major technical problems, including broken localhost connections and non-functional recovery tools.

The issues stem from update KB5066835, rolled out earlier this month as part of the company's regular security cycle.

According to Windows Latest, the patch disrupts locally hosted network connections, meaning applications or web servers that rely on localhost (127.0.0.1) can no longer communicate properly.

The publication stated that Microsoft has acknowledged the issue and confirmed that a hotfix is being released to address it.

However, the rollout may take up to 48 hours before it becomes visible to all affected devices.

Technical Fault Traced to HTTP.sys Regression

The bug appears to originate from a regression in HTTP.sys, the kernel-mode HTTP server used by Windows to process local and web-based requests.

Windows Latest reported that when a browser or application tries to connect to HTTP/2 services hosted on localhost, HTTP.sys mishandles the handshake process and resets the connection.

This fault has impacted developers and IT professionals who depend on Internet Information Services (IIS), ASP.NET, or similar frameworks for testing and hosting applications.

Ongoing Issues Reported

Windows 11 KB5066835 is causing a series of problems for some users on versions 24H2 and 25H2. Among the most common reports:

  • The October 2025 Patch Tuesday update fails to install, returning error codes such as 0x800f0922, 0x800f0983, 0x800f081f, 0x80071a2d, and 0x800f0991.
  • File Explorer document previews are blocked in the Preview pane due to a false security warning.
  • Certain Logitech peripherals have stopped working correctly.
  • Mouse and keyboard devices are unresponsive in WinRE (Windows Recovery Environment).

Users encountering installation failures are advised to download the patch manually from the Microsoft Update Catalog or use the Media Creation Tool for an in-place upgrade. Internet "fixes" circulating in forums are strongly discouraged, as they appear ineffective or risky.

Windows Recovery Environment Rendered Unusable

A separate, equally serious problem has also surfaced. The same update has effectively disabled USB keyboards and mice within the Windows Recovery Environment (WinRE), leaving users unable to troubleshoot or repair their systems if they encounter startup issues.

Windows Recovery Environment (WinRE), as the name suggests, is a built-in suite of tools that allows users to diagnose problems, boot into Safe Mode, or access system restore options. It is a crucial component of Windows—but under the new bug, USB peripherals stop working entirely, meaning users cannot navigate the recovery interface.

Windows Latest confirmed that the fault originates from the October build of Windows 11, noting that the issue 'renders WinRE useless because a bug blocks the mouse or keyboard from working.'

Users Advised to Wait for the Fix

While some users have shared unofficial workarounds online, Windows Latest and The Register both caution against manual registry or system modifications, which can make Windows unstable or prevent it from booting.

Microsoft has not yet issued a formal statement beyond acknowledging the issue, but reports suggest an emergency update is being distributed and should reach most affected systems within the next few days.

Users are advised to check Windows Update regularly and reboot their PCs once the patch becomes available.

Wider Context

The disruption follows Microsoft's decision earlier this month to end free security updates for Windows 10, affecting around 500 million users worldwide.

Those who wish to continue receiving protection can subscribe to the Extended Security Updates (ESU) programme until 2026.

The back-to-back issues highlight 'how fragile Microsoft's ecosystem still is,' even as the company continues to push users toward its latest operating system.

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