Microsoft's September patches break RDP, USB audio, and Excel paste

Microsoft’s September 2026 update cycle fixed security holes but introduced a cluster of functional regressions across Windows and Office. Remote Desktop Services took the worst hit: on Windows 11 26H1, Windows Server 2012, and other builds, connections drop after a few minutes, servers hang at the ‘Please wait for the Remote Desktop Configuration’ screen, and management tools like MMC, the RDS Licensing Diagnoser, and File Explorer freeze up. The only stopgap is restarting affected VMs to briefly restore connectivity while Microsoft works on a permanent fix.

Audio and productivity were also collateral damage. USB Audio Class 1.0 devices on Windows 11 24H2, 25H2, and 26H1 can lose sound entirely, break volume and settings controls, or fail on multichannel output; dropping to two-channel mode helps some users. Separately, the paste function silently dies in Excel 2016 through 2024—content simply doesn’t move, with no beep or error to signal the failure. That regression stems directly from patches closing remote code execution and information disclosure flaws in Excel.

The episode underscores the recurring tension in Microsoft’s patch pipeline: the documented workarounds for the Excel bug include uninstalling the security update via command line, which trades the vulnerability fix back for working software. For admins, that leaves an uncomfortable choice between security and functionality until Microsoft ships proper corrections, none of which yet have firm timelines.