Windows 11 25H2 · KB5124008 · Build 26200.9445

What changed

Microsoft published the 2026-09-08 security baseline for Windows 11 25H2 with KB5124008 and build 26200.9445.

Technical details

• KB5124008 security update for Windows 11 25H2
• OS build 26200.9445

Why it matters

The current Microsoft KB and OS build are the baseline for deployment rings, compliance and servicing reports.

Known limitations

• Review the linked Microsoft KB for current known issues, safeguards and resolved issues.

Now check

• Validate KB5124008 and build 26200.9445 in the pilot ring
• Review the Microsoft KB known-issue section
• Confirm servicing stack and update media prerequisites