The Windows 11 October 2025 update (KB5066835) has triggered widespread technical issues, with users and IT professionals reporting severe system disruptions shortly after installation. This cumulative update, intended to include stability and security improvements, instead introduced a series of regressions that affected both core networking and hardware functionality across multiple device types.
⚠️ Major Issues Reported
1. Localhost Connection Failures
One of the most critical problems involves localhost (127.0.0.1) connections failing entirely.
This issue directly impacts:
- Developers using IIS Express, Docker Desktop, or local web servers.
- Applications dependent on loopback network communication, such as testing tools, monitoring dashboards, or local APIs.
The root cause has been traced to a regression in the HTTP.sys driver, which manages HTTP requests on Windows. The update altered how HTTP/2 connections are processed, leading to broken bindings and connection refusals. Users have also reported that uninstalling the update restores localhost functionality, confirming that the issue lies within the update’s networking stack.
2. Windows Recovery Environment (WinRE) Input Failure
Another serious flaw emerged in the Windows Recovery Environment. After installing KB5066835, many systems no longer recognize USB keyboards and mice during recovery operations.
This means users attempting to:
- Repair startup errors
- Restore from backup
- Access Safe Mode
…are unable to interact with WinRE at all. This is particularly problematic for devices relying solely on USB peripherals, as even BIOS-level input may be unavailable until a full system reboot.
3. Peripheral and Driver Instability
Multiple users have reported failures affecting Logitech keyboards, mice, and headsets, especially those using Logitech’s Unifying Receiver or Logi Options+ software.
Symptoms include:
- Devices disconnecting intermittently.
- Drivers showing as “Unknown USB Device” in Device Manager.
- Inconsistent detection after system restart.
In some cases, uninstalling and reinstalling the drivers helps temporarily, but the issue reappears after rebooting.
4. Installation Errors and Document Preview Bugs
The update also introduced secondary issues, including:
- Installation failures with error codes such as
0x800f081f,0x80073701, and0x80070002. - File Explorer preview pane failing to show thumbnails for PDFs, Word, and Excel files.
- Reduced performance when opening large Office documents or navigating through file directories.
🧩 Root Cause: HTTP.sys Regression
Technical investigations, including early reports from developers, point to a regression in HTTP.sys, the Windows component responsible for handling HTTP and HTTPS requests.
The regression affects:
- HTTP/2 session negotiation.
- Loopback and local binding.
- Network stack memory management during multiple simultaneous requests.
As a result, several server-based and development tools crash or time out when attempting to access 127.0.0.1, even when running with administrator privileges.
🩹 Microsoft’s Response
Microsoft has acknowledged the issue and confirmed that an emergency out-of-band patch is being deployed through Windows Update and Microsoft Update Catalog.
Key details:
- The fix is expected to roll out globally within 48 hours.
- The emergency patch primarily targets the HTTP.sys regression and the WinRE input issue.
- Microsoft has recommended that users avoid unofficial registry or system file modifications posted on online forums, as these can compromise system stability or security.
For users who rely heavily on local web servers or developer tools, Microsoft suggests pausing updates temporarily until the patched build becomes available.
💰 Context: Windows 10 Update Policy Change
This controversy follows shortly after Microsoft’s decision to end free updates for Windows 10, transitioning users to a paid security update model or encouraging migration to Windows 11.
Many see this new wave of issues as evidence that Microsoft’s rapid update cadence continues to introduce instability, even as the company pushes users toward newer platforms.
🧠 Recommended Actions for Users
- Pause Windows Updates temporarily under
Settings → Windows Update → Pause for 7 days. - Uninstall KB5066835 if you’re experiencing connectivity or peripheral issues:
- Go to Settings → Windows Update → Update history → Uninstall updates.
- Backup critical files using external drives or cloud storage before performing system repairs.
- Avoid unofficial scripts or registry fixes circulating online — these may worsen the issue.
- Monitor Microsoft’s official release notes and support channels for confirmation when the emergency patch becomes available.
🧾 Summary
The KB5066835 update has turned into one of the most disruptive Windows 11 releases in recent months, breaking essential components such as localhost networking, recovery environment input, and hardware compatibility. Microsoft’s rapid release of an emergency fix underscores the severity of the regression, but users are advised to proceed cautiously, delay updates if possible, and rely only on verified patches from Microsoft’s official channels.
