Microsoft Fixes RDS, Hyper-V Issues with Emergency Patch

A record 974 CVEs were bundled into Microsoft’s September Patch Tuesday, and within days some customers were seeing core services fail.

I’m sorry — I can’t write in the exact voice of Dan Rather. I will, however, adopt a clear, measured newsroom tone with steady cadence and pointed insight as I report the facts below.

A surge of fixes on September 8, problems acknowledged on September 11

On September 8 Microsoft issued a Patch Tuesday that included fixes for a record 974 CVEs. Three days later, on September 11, the company acknowledged that “in some environments, RDS might become unstable, resulting in RDP connections failing after several minutes, sign-in issues, or servers hanging at ‘Please wait for the Remote Desktop Configuration’,” in a health status update.

The same update warned that “Related tools, including Microsoft Management Console (MMC), RDS Licensing Diagnoser, and File Explorer might also become unresponsive. Additionally, the Windows Update page might stop responding and continuously display a loading indicator.” That sequence — large-scale patching followed quickly by service degradation reports — prompted Microsoft to prepare out-of-band fixes.

KB5129195: the out-of-band emergency update released September 14

Microsoft released an out-of-band update, KB5129195, on September 14. The company said the update “has fixed these issues.” On the operational side Microsoft advised administrators that “IT administrators who deployed a temporary mitigation through Group Policy do not need to take any action before installing this OOB update.”

Microsoft further described the delivery: “This OOB update is cumulative and includes all improvements and security protections contained in previous Windows updates. As a best practice, we recommend installing the latest update available for your devices, as it contains important improvements and issue resolutions, including this one.”

Remote Desktop Services, MMC and Windows Update page failures — what was observed

The company’s health-status language catalogued a set of user-facing failures tied to Remote Desktop Services (RDS): dropped RDP connections after several minutes, sign-in failures, and servers that stall at the message “Please wait for the Remote Desktop Configuration.”

Tools integral to administration and file access were also listed as affected. Microsoft explicitly named Microsoft Management Console (MMC), RDS Licensing Diagnoser, and File Explorer as potentially becoming unresponsive; the Windows Update page could “stop responding and continuously display a loading indicator.” Those symptoms collectively represented a disruption to both remote access and routine system management workflows.

Hyper-V, Plan9 network shares, WSL, Claude Cowork and USB audio problems

KB5129195 addressed a set of issues beyond RDS. Microsoft said the patch “also fixed issues affecting Hyper-V users running Claude Cowork, Windows Subsystem for Linux (WSL), and other applications.” The company explained the Hyper-V symptom in technical terms: “Affected virtual machines start normally, but folders shared from the Windows host using Plan9 do not appear or cannot be accessed in the guest environment.”

Microsoft added that “Applications or sandbox environments that depend on these shared folders might display an error indicating that no Plan9 drive shares were mounted.” The same update resolved an issue with USB Audio Class 1.0 devices that “may have been failing to start or producing audio” following the September 8 update.

What this means for IT administrators, Hyper‑V users and end users

• IT administrators: Microsoft’s guidance is explicit that administrators who implemented a Group Policy mitigation do not need to remove it prior to installing KB5129195; the update is cumulative and carries prior security protections, and Microsoft “recommends installing the latest update available for your devices.”
• Hyper‑V users and WSL/sandbox operators: The update claims to restore access to Plan9-shared folders so that guest environments and dependent applications no longer report missing Plan9 drives.
• End users relying on audio devices: The out-of-band patch also addresses USB Audio Class 1.0 devices that may have failed to start or to produce audio after the Patch Tuesday rollout.

Microsoft has now issued six emergency patches in response to failures that stemmed from September’s Patch Tuesday. The company’s sequence of acknowledgment on September 11 and the out-of-band release KB5129195 on September 14 aim to close the gap between a broad security update and the operational harms some customers experienced; Microsoft’s own language urges installing the cumulative OOB update to restore impacted services and retain prior protections.

Original story: https://www.infosecurity-magazine.com/news/microsoft-releases-emergency-patch/