Patch tracker / KB5122880
KB5122880: Windows 11 Version 23H2 Security Update (September 2026)
KB5122880 is a Critical security update for Windows 11 Version 23H2, released 2026-09-08. It closes 611 CVEs with a maximum CVSS of 9.8. At least one of them is actively exploited (CISA KEV), so it is urgent, and Microsoft lists 4 known issues: test it before broad deployment. It is the sixth largest of the 54 updates Microsoft shipped that month, by CVEs closed.
Before you deploy: Microsoft lists 4 known issues for this update.
Our data comes from Microsoft, CISA and other public sources, and it can be wrong or out of date. If you are unsure, check the linked source before you act, and tell us when we are wrong so we can fix it.
Update summary
Fixes 611 CVEs. At least one is actively exploited (CISA KEV). Most severe CVSS 9.8 (Critical). EPSS exploit probability up to 2.8%. Among the top half of tracked Microsoft updates by EPSS exploit probability.
A newer security update for Windows 11 Version 23H2 for ARM64-based Systems has shipped since this one: KB5126653 (2026-10-13). For cumulative update families the newer package includes these fixes, so installing that one is usually the shorter path. Verify against your own update rings before you skip this package.
Microsoft documents 4 known issues with this update.
- USB Audio Class 1.0 devices with error Code 10 or no output
- Host folder shares might be unavailable in Hyper-V-based Linux VMs
- Remote Desktop Services might stop responding after September 2026 security update
Senserva AI Opinion and rich prompt for KB5122880
Copy this prompt into Claude, ChatGPT, or Copilot. The facts are included, sourced from this page.
Full tracking and change history for KB5122880
- Released
- 2026-08-11
- Last changed
- 2026-11-03
- Changes tracked
- 11
Senserva began recording day-to-day change history on 2026-07-07, and refreshes it several times a day. Release dates are historical where Microsoft publishes them; revision history is tracked from that date forward, so it does not include changes made before then.
Microsoft revised KB5122880 on 2026-10-13: CVEs fixed 602 to 611.
- 2026-09-12 CVEs fixed 601 to 602
- 2026-10-13 CVEs fixed 602 to 611
Recorded by Senserva on the dates shown, from the MSRC release feed. This is what moved and when, which neither the vendor advisory nor NVD publishes.
Check if KB5122880 is installed
Elevated PowerShell. No output means it is not installed.
Known issues, from Microsoft
Quoted from Microsoft's support article for KB5122880 (checked 2026-11-05). Microsoft lists 4 known issues. Verify against the article before acting.
1. USB Audio Class 1.0 devices with error Code 10 or no output
Symptoms
After installing the September 8, 2026, Windows security update, some USB Audio Class 1.0 devices might fail to start or produce audio. Affected devices might experience one or more of the following symptoms:
The device displays an error in Device Manager: "This device cannot start (Code 10).”
No audio output.
Volume controls are unresponsive or remain at zero.
Sound settings are unresponsive or unavailable.
Some devices might function in standard stereo configurations but fail when using multichannel audio features, including 8-channel or 3D audio modes. Some customers have reported that they're able to restore audio in these cases by switching to 2-channel mode.
This issue is limited to USB Audio Class 1.0 devices.
Resolution
This issue is partially resolved in the out-of-band (OOB) update released on September 14, 2026. This OOB update resolves the symptoms experienced on devices using 8-channel or 3D audio modes. Microsoft is working to address the other symptoms and will provide more information when it is available.
IT administrators who need an immediate workaround for the symptoms not addressed yet by the OOB update should contact Microsoft Support for Business for assistance.
2. Host folder shares might be unavailable in Hyper-V-based Linux VMs
Symptoms
After installing the September 2026 security update KB5122880 , applications that use HCS-managed virtual machines might experience issues when sharing host folder with Linux VMs using Plan9. Affected virtual machines start normally, but folders shared from the Windows host using Plan9 do not appear or cannot be accessed in the guest environment.
Applications or sandbox environments that depend on these shared folders might display an error indicating that no Plan9 drive shares were mounted. Claude Cowork and the Windows Subsystem for Linux (WSL) are two of the applications affected by this issue. Standard Hyper-V virtual machines that do not use the Plan9 feature are not affected by this issue.
Next steps
Microsoft is working on a resolution and will update this documentation when more information is available.
3. Remote Desktop Services might stop responding after September 2026 security update
Symptoms
After installing the September 2026 Windows security update, some organizations might experience issues with Remote Desktop Services (RDS).
In some environments, RDS might become unstable, resulting in RDP connections failing after several minutes, sign-in issues, or servers hanging at "Please wait for the Remote Desktop Configuration". Related tools, including Microsoft Management Console (MMC), RDS Licensing Diagnoser, and File Explorer might also become unresponsive. Additionally, the Windows Update page might stop responding and continuously display a loading indicator.
Note
This issue does not affect Windows 365 or Azure Virtual Desktop.
Resolution
This issue is resolved in Windows updates released on and after September 14, 2026 such as KB5129242 . We recommend you install the latest Windows update for your device as it contains important improvements and issue resolutions, including this one.
4. File History might stop working after installing September 2026 Windows update
Symptoms
After installing the September 2026 Windows security update KB5124008 , some customers using File History, might be unable to create or update backups. File History, available through Control Panel > System and Security > File History , is used to back up files to an external drive or network location. Affected devices might incorrectly display a "Reconnect your drive" message even when a compatible backup drive is connected and functioning properly. Additionally, the "Last Backup" timestamp might not update, and previously backed up files might show "No previous version available." In some cases, Event Viewer might record application crash events referencing FileHistory.exe and KERNELBASE.dll .
Resolution
This issue is resolved in Windows updates released on and after October 13, 2026 such as KB5126653 . We recommend you install the latest Windows update for your device as it contains important improvements and issue resolutions, including this one.
Windows release health for this update
From Microsoft's Windows release health for Windows 11, version 23H2, checked 2026-11-10. Microsoft's issue text is linked from each title.
Issues Microsoft traces to this update
- USB audio devices might fail to start or produce no sound
Resolved. Microsoft last updated it 2026-10-13 11:02 PT.
CVEs fixed by this update
Sorted exploited-first, then by CVSS. Every CVE links to its Senserva page with the full risk facts, references, and a ready-to-paste AI prompt.
Scope and sources
- Affected products
- Also released in September 2026
KB5122871
687 CVEs · Critical · exploitedKB5122876
623 CVEs · Critical · exploitedKB5122878
575 CVEs · Critical · exploitedKB5122882
648 CVEs · Critical · exploitedKB5123065
400 CVEs · Critical · exploitedKB5123066
425 CVEs · Critical · exploitedKB5123099
562 CVEs · Critical · exploitedKB5124008
638 CVEs · Critical · exploitedThe full month, summarized: Microsoft Patch Tuesday.
- Authoritative references
See this and every Microsoft update ranked by real-world risk on the Microsoft Patch Tracker.