This cumulative update for Windows 11, version 26H1 (KB5132059) includes the latest security fixes and improvements, along with non-security updates from last month's optional preview release. Visit the Windows release health dashboard for the latest status on this release.
Important
Because of minimal operations during the Western holidays and the upcoming new year, there will be no December 2026 non-security preview update in the second part of the month. Normal monthly servicing for both security and non-security preview updates will resume in January 2027.
Improvements
This update includes new features and quality improvements that were part of the following update:
- October 13, 2026—KB5127646 (OS Build 28000.3231)
- October 26, 2026—KB5134134 (OS Build 28000.3237) Out-of-band
- October 28, 2026—KB5127653 (OS Builds 28000.3365) Preview
The following summary outlines key quality improvements addressed by this update. The bold text within the brackets indicates the item or area of the change.
[Security updates] This update provides security improvements. For more information about the security vulnerabilities resolved by this update, see the Security Update Guide
[Secure Boot] This update includes additional high confidence device targeting data, increasing coverage of devices eligible to automatically receive new Secure Boot certificates. Certificate deployment via Windows updates continues across supported PCs and non-managed business devices in the coming months.
[Audio (known issue)] - Fixed: USB Audio 1.0 devices might fail to start and display error code 10 in Device Manager after installing a recent security update.
[Printing] - Fixed: Adding a printer published in Active Directory through Settings > Bluetooth & devices > Printers & scanners > Add device might fail with error 87, "The parameter is incorrect." This issue was introduced by the October 2026 update and does not generally affect existing printers or printing.
[Security] This update improves NTLM security by enabling clients to offer NTLM message signing by default for non-anonymous connections. This change helps reduce exposure to NTLM relay attacks and provides auditing to identify connections that are not using signing. To learn more, see NTLM signing security improvements in Windows.
[Date and Time] This update adjusts daylight saving time (DST) rules for Cuba for the extended 2026-2027 DST period. Cuba remains on UTC-04:00 and doesn't observe the November 2026 and March 2027 transitions. It returns to UTC-05:00 in November 2027 and resumes its regular seasonal schedule in 2028.
- For the latest DST and time zone guidance, see the Daylight Saving Time & Time Zone Blog.
[Remote Desktop] Fixed: Remote Desktop (RDP) connections might fail due to a certificate mismatch after installing the October 2026 non-security preview update.
[Windows PowerShell] This update strengthens security for PowerShell script signing and signature verification by introducing stricter encoding validation. As a result, scripts containing invalid UTF-8 encoding might fail signature validation, even if they were previously accepted. To resolve this issue, review the affected scripts, save them using valid UTF-8 encoding with a byte order mark (BOM), and sign them again. For further guidance, see Encoding Guidance for Signed PowerShell Scripts.
If you've already installed previous updates, your device will download and install only the new updates included in this package.
Component updates
AI components
This release updates the following AI components to version 1.2610.1071.0: Image Search, Content Extraction, Semantic Analysis, and Settings Model.
To learn more, see Release information for AI components.
Servicing stack update
Microsoft combines the latest servicing stack update (SSU) for your operating system with the latest cumulative update (LCU). This Windows update includes KB5132687 (Build 28000.3501), which improves the reliability of the Windows update installation process. To learn more about SSUs, see Servicing stack updates.
Known issues in this update
Microsoft is not currently aware of any issues with this update.
How to get this update
Before you install this update
Servicing Stack Update (SSU): You must have installed servicing stack update version 28000.1575 or later before installing this update. To determine the latest SSU installed on your device, run DISM /Online /Get-Packages | findstr /i "ServicingStack" from an elevated command prompt. The Package Identity line returned must be version 28000.1575 or later.
Deployment
If you deploy dynamic updates such as this update to an existing Windows image, ensure the boot.stl file is included as part of the installation media. Failure to include the file might prevent devices from successfully starting from the installation media and can result in error code 0xc0430001.
Note
The boot.stl file is used during Secure Boot validation and must match the Windows version and architecture of the image you are updating.
To ensure the boot.stl file is included as part of the installation media, do one of the following:
- Use the Update WinPE script to update an existing Windows image. (Recommended)
- Manually copy the boot.stl file from the device Windows\Boot\EFI folder to the corresponding folder on your installation media before deploying the update.
For information about how to apply Dynamic Update packages to existing Windows images, see Update Windows installation media with Dynamic Update.
Install this update
To install this update, use one of the following Windows and Microsoft release channels.
| Available | Next Step |
|---|---|
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This update downloads and installs automatically from Windows Update and Microsoft Update. |
File information
For a list of the files provided in this update, download the file information for cumulative update KB5132059.
For a list of the files provided in the servicing stack update, download the file information for the SSU (KB5132687) - version 28000.3501.
Related topics
Windows monthly updates explained
Description of the standard terminology used for Microsoft software updates