Patch intelligence record
Windows 11 26H1 (Build 28000.2954)
Current reports mention update/install failure. This page covers one cumulative update, not the whole 26H1 servicing train; reports about a later update are counted on that update's own page.
Recommendations
- Pause updates if this machine is doing deadline-sensitive or production work.
- Check Microsoft's known-issue and safeguard-hold list for this KB before installing.
- Keep the uninstall path in mind: a cumulative update can be removed from Settings > Windows Update > Update history for a limited window after installation.
Current reports mention update/install failure in windows update.
Too few reports for a firm verdict yet — treat this as early evidence.
- Accepted reports
- 1
- Latest evidence run
- Oct 6, 2026
- Healthy sources
- 2 fresh (success / no reports) · need 2
- Microsoft Q&A (search) Completed last checked Oct 6, 2026
- techcommunity windows sitemap Checked — no reports found last checked Oct 6, 2026
Monitoring reflects community-evidence collection health for this exact release — an absence of reports is not a safety guarantee, and this is separate from the AUXSAYS verdict.
Vendor Known Issues — 4 active vendor-known issues
4 active 1 resolved
Official vendor Release Health status. Not counted as community reports. Official source ↗
Official Patch Notes — vendor release notes captured from the official source
Windows 11 26H1 cumulative update, OS build 28000.2954 (KB5124012). Released 2026-09-08 on the General Availability Channel. Update type 2026-09 B. This is the official Microsoft Windows release-health entry (learn.microsoft.com/windows/release-health). Known-issue and safeguard-hold details are published on the per-version Windows release-health status page. Microsoft Release Health status (official) for Windows 11.
Windows 11 in these notes: .
Windows 11 26H1 cumulative update, OS build 28000.2954 (KB5124012). Released 2026-09-08 on the General Availability Channel. Update type 2026-09 B. This is the official Microsoft Windows release-health entry (learn.microsoft.com/windows/release-health). Known-issue and safeguard-hold details are published on the per-version Windows release-health status page.
Technical Details
- Released
- Sep 8, 2026
- File size
- Official source checked
- Oct 6, 2026
- Official notes checked
- Oct 6, 2026
Checksum
Use these hashes to verify downloaded installers match the files published with the official release.
User Reports / Sources (1)
User report sources used for the current read.
- Microsoft Learn Q&A. (2026, September 9). KB5124008 (Win 11 25H2, build 26200.9445) breaks Plan9/virtiofs host share attachment for Hyper-V based sandbox VMs - Microsoft Q&A. microsoft learn qna Issue: update/install failure in windows update Workflow: windows update
Official sources
- Microsoft. (2026, September 8). Windows 11 release information.release health
- Microsoft. (2026, September 8). Windows release health.release health
- Microsoft. Download page.download