On October 14, 2025, Microsoft released security update KB5066835 for Windows 11 versions 24H2 and 25H2, as well as Windows Server 2025. This update, identified as OS Build 26100.6899, has led to a critical issue where USB keyboards and mice become unresponsive within the Windows Recovery Environment (WinRE).
Impact on Windows Recovery Environment
WinRE is an essential tool for users to repair boot failures, reset PCs, or restore from backups. Post-update, while USB input devices function correctly during regular Windows sessions, they fail entirely within WinRE. This malfunction prevents users from navigating recovery options, effectively rendering the recovery environment unusable.
User Reports and Microsoft’s Acknowledgment
Shortly after the update’s deployment, users began reporting that their USB mice and keyboards were unresponsive in WinRE, obstructing access to critical recovery menus and commands. Microsoft publicly acknowledged this issue on October 17, 2025, emphasizing the urgency for users who depend on reliable recovery tools.
Additional Issues Stemming from KB5066835
Beyond the WinRE input device problem, KB5066835 has introduced several other complications:
– Network Connectivity Problems: Users have encountered issues with localhost connections failing to establish, complicating local development and testing processes.
– Installation Failures: Some users report cryptic errors during the update installation, necessitating manual rollback to previous versions.
– File Explorer Malfunctions: The preview pane in File Explorer has become blank or unresponsive, hindering productivity.
– System Performance Degradation: Users have noted sluggish performance, including delayed application launches and erratic multitasking behavior.
These issues have been reported across a broad spectrum of devices, from consumer laptops to enterprise servers, indicating the update’s extensive impact.
Implications for IT Administrators
For IT professionals, the inability to use WinRE due to unresponsive input devices poses significant risks during system outages. This limitation can escalate minor technical issues into major operational downtimes, affecting business continuity.
Microsoft’s Response and Interim Solutions
Microsoft has acknowledged these flaws and is actively working on developing fixes, with resolutions expected in the coming days. In the meantime, the company advises the following:
– Avoid Using WinRE: If possible, refrain from entering the Windows Recovery Environment until a fix is implemented.
– Alternative Recovery Methods: Utilize alternative recovery options, such as booting from installation media that supports functional peripherals.
– Uninstall KB5066835: For those already affected, uninstalling the update via Settings > Update & Security > View update history can provide temporary relief. However, this action may expose systems to previously addressed security vulnerabilities.
Historical Context and User Recommendations
This incident is reminiscent of past Windows update issues that have disrupted system functionality. Users are reminded of the importance of pausing automatic updates during critical periods to prevent potential disruptions. As Microsoft rolls out patches, affected individuals should monitor official channels for updates to restore full system functionality.
