Windows Server 2019 KB5129238
Windows Server 2019 build 17763.9247 (KB5129238) is an out-of-band update released to resolve a Remote Desktop Services issue introduced by the September 2026 security update. Affected environments could experience RDS instability, failed RDP connections, sign-in problems, or servers becoming unresponsive during Remote Desktop configuration. The update incorporates the fixes and improvements from the September 8 security update KB5122876.
What's new
Microsoft Windows Server 2019 build 17763.9247 (KB5129238) is an out-of-band cumulative update released following the September 2026 security update.
What's new- Fixes a Remote Desktop Services issue introduced after installing the September 2026 security update KB5122876.
- Resolves RDS instability that could cause RDP connections to fail after several minutes.
- Addresses Remote Desktop sign-in failures in affected environments.
- Fixes cases where servers could become unresponsive at the "Please wait for the Remote Desktop Configuration" stage.
- Addresses related responsiveness issues affecting Microsoft Management Console (MMC), RDS Licensing Diagnoser, File Explorer, and Windows Update.
- Includes the fixes and quality improvements previously released with KB5122876 (OS Build 17763.9245).
- Some USB Audio Class 1.0 devices may fail to start or produce audio, display Device Manager error Code 10, or have unavailable or unresponsive volume controls.
Organizations affected by Remote Desktop Services instability after the September 2026 security update should prioritize deployment of KB5129238 after expedited validation. This update is particularly important for Windows Server 2019 environments that rely heavily on Remote Desktop Services or RDP-based administration.
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