Patch intelligence record
Windows 11 26H2 (Build 26300.9457)
Current reports mention update/install failure. This page covers one cumulative update, not the whole 26H2 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
- 2
- 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 — No vendor-known issue data captured for this patch.
AUXSAYS has not captured official issue data for this patch. This does not indicate the vendor has no issues. Not counted as community reports.
Official Patch Notes — vendor release notes captured from the official source
Windows 11 26H2 cumulative update, OS build 26300.9457. Released 2026-09-29 on the General Availability Channel. 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.
Windows 11 in these notes: .
Windows 11 26H2 cumulative update, OS build 26300.9457. Released 2026-09-29 on the General Availability Channel. 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 29, 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 (2)
User report sources used for the current read.
- Microsoft Learn Q&A. (2026, October 3). Windows Activation - Microsoft Q&A. microsoft learn qna Issue: update/install failure in windows update Workflow: windows update
- Microsoft Learn Q&A. (2026, October 5). After Windows 11 26H2 update: apps lose saved logins, WhatsApp won't open (DPAPI "Could not get the master key") - cause and fix - Microsoft Q&A. microsoft learn qna Issue: update/install failure in windows update Workflow: windows update
Official sources
- Microsoft. (2026, September 29). Windows 11 release information.release health
- Microsoft. (2026, September 29). Windows release health.release health
- Microsoft. Download page.download