Microsoft has issued an emergency out-of-band update for Windows 11 24H2 and 25H2 after September's Patch Tuesday, which fixed almost 1,000 vulnerabilities across the company's products, introduced fresh problems of its own. The follow-up patch resolves issues affecting Remote Desktop Services and shared host folders on certain Hyper-V-based Linux virtual machines, though a fault affecting some USB audio devices remains only partially addressed.

The update restores multichannel playback on USB Audio Class 1.0 devices that had been stuck working only in stereo, but other affected devices may still lose sound entirely, suffer unresponsive volume controls, or show a "This device cannot start (Code 10)" error, with Microsoft saying a full fix is still being worked on. The cumulative update also adds protection against CVE-2026-62721, an elevation-of-privilege flaw in the Windows User-Mode Power Service. Separately, September's security updates for Excel broke the Paste function on some installations, a bug Microsoft has yet to fix.