September's Windows 11 patch needs an emergency patch of its own

Microsoft has delivered an emergency patch for Windows 11's September update, which itself addressed over 1,000 security vulnerabilities but inadvertently introduced several new issues. The problems are primarily linked to USB Audio Class 1.0 devices, Remote Desktop Services, and host folders shared with specific Hyper-V-based Linux virtual machines using Plan9.

While the issues with Hyper-V and Remote Desktop Services have been resolved, the USB audio problems persist. The update restores multichannel playback for devices that previously functioned correctly in stereo, but other affected devices may remain silent, exhibit unresponsive volume controls, or display a "This device cannot start (Code 10)" error in Device Manager.

Microsoft has acknowledged the issue and is actively working on a resolution, promising to update its documentation as more information becomes available. In the meantime, users with silent USB devices are advised to wait for the forthcoming fix.

The cumulative update also incorporates safeguards against CVE-2026-62721, an elevation-of-privilege vulnerability found in the Windows User-Mode Power Service. However, a separate security patch for Excel, released concurrently, has encountered its own set of problems. The update inadvertently broke the seldom-used Paste function in Excel, frustrating some users who were left without a working method to copy and paste data in the commonly utilized software.

Despite the setbacks, Microsoft's efforts to ensure its patches don't disrupt users' workflows have been met with considerable appreciation. Some users have praised the company's approach, recognizing that such high-stakes updates inevitably involve rigorous testing. Others have suggested that the issues might stem from a lack of user feedback or bug reports, emphasizing the importance of communication channels for reporting software glitches.