Microsoft has released an out-of-band security update KB5129194 for Windows 11, version 26H1, after Patch Tuesday. The update closes two privilege escalation vulnerabilities, restores RDP connection stability, and multichannel audio on USB Audio Class 1.0 devices.
The out-of-band update KB5129194 (Build 28000.2956) for Windows 11, version 26H1, closes two vulnerabilities and fixes issues that appeared after the September release. The update is cumulative and includes all security fixes and improvements from the September 8, 2026 security update (KB5124012), as well as the following changes.
- Vulnerability in the power management service. A privilege escalation vulnerability in the Windows User-Mode Power Service has been closed – CVE-2026-62721.
- Vulnerability in Secure Kernel Mode. A privilege escalation vulnerability in Secure Kernel Mode has been closed – CVE-2026-85921.
- Instability of Remote Desktop Services. Instability in Remote Desktop Services (RDS) has been fixed, which after installing the September update caused RDP connections to drop and system tools to stop responding.
- Access to shared folders of Linux virtual machines. Access to shared folders of Linux virtual machines that connect via the Plan 9 protocol has been restored.
- Multichannel audio on USB Audio Class 1.0 devices. Support for multichannel audio on USB Audio Class 1.0 devices has been restored.
Known issues. On some USB Audio Class 1.0 devices, audio may disappear, Code 10 appears in Device Manager, and volume adjustment stops working. Microsoft is working on a fix.
Update KB5129194 is downloaded and installed automatically via Windows Update. The package is also available for manual download from the Microsoft Update Catalog. To install via Windows Update, go to Settings > Windows Update and click Check for updates. A restart of the computer is required to complete the installation.
| Feature / Change | Performance Increase / Decrease | Optimization | PC Speed Impact | Gaming Optimization | Micro Explanation |
|---|---|---|---|---|---|
| Vulnerability in the power management service (CVE-2026-62721) | ⚪ 0% (no performance change) | 🟢 High (security hardening) | ⚪ No measurable impact | ⚪ No impact | Closes a privilege escalation hole in the Windows User-Mode Power Service; purely a security fix. |
| Vulnerability in Secure Kernel Mode (CVE-2026-85921) | ⚪ 0% (no performance change) | 🟢 High (kernel security hardening) | ⚪ No measurable impact | ⚪ No impact | Patches a privilege escalation flaw in Secure Kernel Mode; reduces attack surface at the core of the OS. |
| Instability of Remote Desktop Services | 🟢 +15–25% stability of RDP sessions | 🟢 High (fixes regression from September update) | 🟢 Moderate (no more dropped RDP sessions and hung system tools) | ⚪ No impact | Resolves crashes where RDP connections dropped and system utilities stopped responding after the September patch. |
| Access to shared folders of Linux virtual machines (Plan 9) | 🟢 +100% restored functionality | 🟢 High (WSL/Hyper-V interoperability) | 🟢 Low–Moderate (file access works again) | ⚪ No impact | Restores Plan 9–based shared folder access between Windows host and Linux VMs. |
| Multichannel audio on USB Audio Class 1.0 devices | 🟢 +100% restored functionality | 🟢 Medium (audio stack) | ⚪ No measurable impact | 🟢 Medium (better multichannel game audio over USB) | Brings back multichannel audio output on USB Audio Class 1.0 hardware. |
Official announcement on the Microsoft website.
The last 10 Windows updates:
| Update | Build | Version | Windows | Channel | Date |
|---|---|---|---|---|---|
| KB5126657 | 19045.7807 | 22H2 (ESU) | Windows 10 | Stable | 2026-10-13 |
| KB5126653 | 22631.7652 | 23H2 | Windows 11 | Stable | 2026-10-13 |
| KB5127646 | 28000.3231 | 26H1 | Windows 11 | Stable | 2026-10-13 |
| KB5127648 | 26300.9711 | 26H2 | Windows 11 | Stable | 2026-10-13 |
| KB5127757 | 28120.3181 | 26H1 | Windows 11 | Experimental | 2026-10-07 |
| KB5127758 | 26220.9606 | 25H2 | Windows 11 | Beta | 2026-10-07 |
| KB5127754 | 28020.3172 | 26H1 | Windows 11 | Beta | 2026-10-07 |
| KB5127753 | 26340.9616 | 26H2 | Windows 11 | Experimental | 2026-10-07 |
| KB5124192 | 28120.3151 | 26H1 | Windows 11 | Experimental | 2026-10-02 |
| KB5124196 | 28020.3142 | 26H1 | Windows 11 | Beta | 2026-10-02 |