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

Microsoft fixes RDP and Hyper-V fallout, but some USB audio stays silent

Microsoft has released an out-of-band update for Windows 11 24H2 and 25H2 after September's record-breaking Patch Tuesday addressed almost 1,000 vulnerabilities across the company's products – and introduced several new problems.

Those problems are related to USB Audio Class 1.0 devices, Remote Desktop Services, and host folders shared with certain Hyper-V-based Linux virtual machines via Plan9.

While the Hyper-V and Remote Desktop Services issues are fixed, there is still work to do on USB audio. The update restores multichannel playback on USB Audio Class 1.0 devices that continued to work in stereo, but other affected devices may remain silent, have unresponsive volume controls, or display "This device cannot start (Code 10)" in Device Manager.

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Owners of devices still giving them the silent treatment were told: "Microsoft is working on a resolution and will update this documentation when more information is available."

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The cumulative update also includes protections for CVE-2026-62721, an elevation-of-privilege vulnerability in the Windows User-Mode Power Service.

Separate September security updates for Excel also broke that rarely used function, Paste, on some installations. Microsoft has yet to issue a fix.

Readers were impressively supportive of Microsoft's efforts to ensure its patches don't disrupt workflows. Paratiritis noted: "The issue with all these versions of Excel is understandable, considering such changes require testing, either manual or automated, which cannot be taken for granted for such cryptic functionality as Paste."

Roj Blake suggested that perhaps somebody had tried submitting a bug report, but was unable to paste the data for some reason. ®