May 12, 2026—KB5087539(OS Build 26100.32860)
Applies To
Release Date:
5/12/2026
Version:
OS Build 26100.32860
This cumulative update for Windows Server 2025 (KB5087539 ), includes the latest security fixes and improvements, along with non-security updates from last month’s optional preview release. To learn more about differences between security updates, optional non-security preview updates, out-of-band (OOB) updates, and continuous innovation, see Windows monthly updates explained. For information on Windows update terminology, see the different types of Windows software updates.
To view the latest updates about this release, visit the Windows release health dashboard or the update history page for Windows Server 2025.
Announcements and messages
This section provides key notifications related to this release, including announcements, change logs, and end-of-support notices.
Windows Secure Boot certificate expiration
Important: Secure Boot certificates used by most Windows devices are set to expire starting in June 2026. This might affect the ability of certain personal and business devices to boot securely if not updated in time. To avoid disruption, we recommend reviewing the guidance and taking action to update certificates in advance. For details and preparation steps, see Windows Secure Boot certificate expiration and CA updates and the Windows Server Secure playbook blog.
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Change date |
Change description |
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May 13, 2026 |
Added Secure Boot release note: This update adds a new SecureBoot folder under C:\Windows on eligible devices. |
Improvements
This security update contains fixes and quality improvements from KB5082063 (released April 14, 2026) and KB5091157 (release April 19, 2026). The following summary outlines key issues addressed by this update. Also, included are available new features. The bold text within the brackets indicates the item or area of the change.
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[Secure Boot]
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With this update, Windows quality updates include additional high confidence device targeting data, increasing coverage of devices eligible to automatically receive new Secure Boot certificates. Devices receive the new certificates only after demonstrating sufficient successful update signals, maintaining a controlled and phased rollout.
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This update adds a new SecureBoot folder under C:\Windows on eligible devices. The folder contains example scripts intended for organizations with IT professionals who actively manage updates across their device fleet. These scripts can be used to detect Secure Boot certificate update status and automate deployment via a safe rollout mechanism in an Active Directory environment. For more information, see Sample Secure Boot E2E Automation Guide.
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[Connectivity] This update improves the reliability of Simple Service Discovery Protocol (SSDP) notifications to help prevent the service from becoming unresponsive.
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[Daylight saving time (DST)] This update supports the 2023 DST change for the Arab Republic of Egypt.
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[Domain controllers] This update improves the performance of the Local Security Authority Subsystem Service (LSASS) on domain controllers when Microsoft Defender is enabled. It reduces CPU and memory usage during Event Tracing for Windows collection of IDL_DRSGetNCChanges events.
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[Remote Desktop (known issue)] Fixed: This update addresses an issue that affects the Remote Desktop Connection security warning dialog. The dialog could render incorrectly in multi-monitor scenario when the monitors had different scaling set. This might occur after installing the April 2026 (KB5082063) security update. For more information, see Understanding security warnings when opening Remote Desktop (RDP) files.
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[Sign-In] After you install the Windows update released on or after March 10, 2026, some users might experience an issue signing in to apps with a Microsoft account. Even when the device has a working Internet connection, a “no Internet” error appears during sign in and prevents access to Microsoft services and apps such as Microsoft Teams.
If you've already installed previous updates, your device will download and install only the new updates included in this package.
For more information about security vulnerabilities, see the Security Update Guide and the May 2026 Security Updates.
Windows Server 2025 servicing stack update (KB5089717) - 26100.32837
This update makes quality improvements to the servicing stack, which is the component that installs Windows updates. Servicing stack updates (SSU) ensure that you have a robust and reliable servicing stack so that your devices can receive and install Microsoft updates. To learn more about SSUs, see Simplifying on-premises deployment of servicing stack updates.
Known issues in this update
Symptom
Some devices with an unrecommended BitLocker Group Policy configuration might be required to enter their BitLocker recovery key on the first restart after installing this update.
This issue only affects a limited number of systems in which ALL of the following conditions are true. These conditions are unlikely to be found on personal devices not managed by IT departments.
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BitLocker is enabled on the OS drive.
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The Group Policy "Configure TPM platform validation profile for native UEFI firmware configurations" is configured, and PCR7 is included in the validation profile (or the equivalent registry key is set manually).
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System Information (msinfo32.exe) reports Secure Boot State PCR7 Binding as "Not Possible".
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The Windows UEFI CA 2023 certificate is present in the device’s Secure Boot Signature Database (DB), making the device eligible for the 2023‑signed Windows Boot Manager to be made the default.
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The device is not already running the 2023-signed Windows Boot Manager.
In this scenario, the BitLocker recovery key only needs to be entered once -- subsequent restarts will not trigger a BitLocker recovery screen, as long as the group policy configuration remains unchanged. For help finding your BitLocker recovery key, see the article, Find your BitLocker recovery key.
Enterprises are recommended to audit their BitLocker group policies for explicit PCR7 inclusion and check msinfo32.exe for their PCR7 binding status before installing this update. (See the Workaround below.)
Workaround
Remove the Group Policy configuration before installing the update (Recommended)
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Open Group Policy Editor (gpedit.msc) or your Group Policy Management Console.
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Navigate to: Computer Configuration > Administrative Templates > Windows Components > BitLocker Drive Encryption > Operating System Drives.
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Set "Configure TPM platform validation profile for native UEFI firmware configurations" to "Not Configured".
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Run the following command on affected devices to propagate the policy change: gpupdate /force
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Run the following command to suspend BitLocker (where BitLocker is enabled on the C: drive): manage-bde -protectors -disable C:
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Run the following command to resume BitLocker (where BitLocker is enabled on the C: drive): manage-bde -protectors -enable C:
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This updates the BitLocker bindings to use the Windows-selected default PCR profile.
A permanent resolution for this issue is planned in a future Windows update. More information will be provided when it is available.
After installing KB5070881 or later updates, Windows Server Update Services (WSUS) does not display synchronization error details within its error reporting. This functionality is temporarily removed to address the Remote Code Execution Vulnerability, CVE-2025-59287.
How to get this update
Before you install this update
Microsoft combines the latest servicing stack update (SSU) for your operating system with the latest cumulative update (LCU). For general information about SSUs, see Servicing stack updates.
Install this update
To install this update, use one of the following Windows and Microsoft release channels.
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Next Step |
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This update downloads and installs automatically from Windows Update and Microsoft Update. |
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This update downloads and installs automatically from Windows Update for Business in accordance with configured policies. |
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To install this release from the Microsoft Update Catalog, follow these instructions:Before you install this update, the standalone package(s) for this update is available from the Microsoft Update Catalog website. This KB contains one or more MSU files that require installation in a specific order. You can install this update using Method 1 (install all MSU files together) or Method 2 (install each MSU file individually, in order). Method 1: Install all MSU files together Download all MSU files for KB5087539 from Microsoft Update Catalog and place them in the same folder (for example, C:/Packages). Use Deployment Image Servicing and Management (DISM.exe) to install the target update. DISM will use the folder specified in PackagePath to discover and install one or more prerequisite MSU files as needed. Updating Windows PC To apply this update to a running Windows PC, run the following command from an elevated Command Prompt:
Or, run the following command from an elevated Windows PowerShell prompt:
Or use Windows Update Standalone Installer to install the target update. Updating Windows Installation media To apply this update to Windows Installation media, see Update Windows installation media with Dynamic Update. Note: When downloading other Dynamic Update packages, ensure they match the same month as this KB. If the SafeOS Dynamic Update or Setup Dynamic Update is not available for the same month as this KB, use the most recently published version of each. To add this update to a mounted image, run the following command from an elevated Command Prompt:
Or, run the following command from an elevated Windows PowerShell prompt:
Method 2: Install each MSU file individually, in order Download and install each MSU file individually either using DISM or Windows Update Standalone Installer in the following order:
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Next Step |
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This update will automatically sync with Windows Server Update Services (WSUS) if you configure Products and Classifications as follows: Product: Microsoft Server operating system-24H2 Classification: Security Updates |
If you want to remove this update
Before you decide to remove this update, see Understanding the risks: Why you should not uninstall security updates.
To remove the LCU after installing the combined SSU and LCU package, use the DISM/Remove-Package command line option with the LCU package name as the argument. You can find the package name by using this command: DISM /online /get-packages.
Running Windows Update Standalone Installer (wusa.exe) with the /uninstall switch on the combined package will not work because the combined package contains the SSU. You cannot remove the SSU from the system after installation.
File information
For a list of the files provided in this update, download the file information for cumulative update 5087539.
For a list of the files provided in the servicing stack update, download the file information for the SSU (KB5089717) - version 26100.32837.
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