KB5126105: Overview with user sentiment and feedback
Last Updated October 21, 2026
Probability of successful installation and continued operation of the machine
Overview
KB5126105 is the September 8, 2026 .NET 9.0 security refresh, moving the runtime to version 9.0.20. It is offered to systems with .NET 9.0 installed on supported Windows client and server versions, and is distributed through Microsoft Update, WSUS, and the Microsoft Update Catalog. Packages are listed for x64, x86, and ARM64 clients and x64 servers. Installing it replaces the prior 9.0.19 runtime.
General Purpose
- Delivers the latest .NET 9.0 security fixes (version 9.0.20).
- Acts as a servicing upgrade: installing 9.0.20 removes 9.0.19 if present.
- Available for Windows x64, x86, and ARM64 clients and x64 Windows Server via Microsoft Update, WSUS, and the Catalog.
- May require a restart if affected files are in use; closing .NET-based applications first is recommended.
- Support eligibility requires being on the latest servicing level.
General Sentiment
No substantive community discussion was found for this specific update, and the input did not include Reddit or windowslatest.com coverage. Routine .NET servicing refreshes like this one typically generate little reported trouble. Based on the lack of reported issues, the update appears low-risk.
Known Issues
Disclaimer: We take measures to ensure that AI-generated content is of the highest possible quality, but we cannot guarantee its accuracy and recommend that users do their own independent research. Generated on 2026-10-21 07:49 PM
