Deploy nowKB5129242OOB
It fixes actively exploited vulnerabilities. Deploy as soon as possible, and check the open known issues on your pilot devices first.
UrgencyCritical · 1 exploited
RiskModerate · 1 mitigated
KB5129242OOBOut-of-band release · 2026-09 OOB
Out-of-band release for Windows 11, version 23H2
Is it safe to deploy?
1Windows version
0CVEs fixed · 0 critical
0Exploited or in CISA KEV
1Open known issues affecting it
—Restart required (per MSRC)
Applies to
From Microsoft's release-information tables| Servicing branch | OS build | Release | Available |
|---|---|---|---|
| Windows 11, version 23H2 | 22631.7584 | OOB 2026-09 OOB | 14 Sep 2026 |
Known issues in this update
Includes issues from the update it builds on- Mitigatedfrom KB5122880Win 11 23H2updated 14 Sep USB audio devices might fail to start or produce no soundSome USB Audio Class 1.0 devices display Code 10 or fail in multichannel audio modes after installing KB5124008.
Issues this update resolves
- Resolvedfrom KB5124012fixed by KB5129194Win 11 26H1, Win 11 25H2, Win 11 24H2 +9updated 17 Sep Remote Desktop Services might stop responding after Sept. 2026 security updateSome Windows devices with Remote Desktop enabled might experience Remote Desktop Services (RDS) instability.
- Resolvedfrom KB5124012fixed by KB5129194Win 11 26H1, Win 11 25H2, Win 11 24H2 +3updated 14 Sep Host folder shares might be unavailable in Hyper-V-based Linux VMsPlan9 host folder shares might not appear in the guest environment after installing the September 2026 security update.
Security fixes
0 Microsoft CVEs · most urgent firstNo CVE fixes listed
MSRC lists no CVEs for this KB in the collected releases; preview (D) and out-of-band updates often carry no new security fixes.