Windows Server 2025 Insider Preview Build 26304 Introduces Windows Defender Application Control Features

Microsoft has unveiled the newest version of Windows Server specifically for participants of the Windows Server Insider Program. This release is designated as build 26304 and marks the beginning of the Windows Server 2025 branding for all present and future Insider builds.

A significant enhancement in this update is the introduction of Windows Defender Application Control for Business (WDAC), which, as indicated by its name, enhances security features for Windows Server 2025. Below is the summary of changes:

New Features

[NEW]Windows Defender Application Control for Business (WDAC)

The Windows Defender Application Control (WDAC) for business introduces a robust security framework that mitigates the attack surface by enforcing a defined list of permissible software. For Windows Server 2025, we are offering a Microsoft-defined ‘default policy’ that can be set up on your server using PowerShell cmdlets, supported by our security configuration platform named ‘OSconfig’.

Preview of Windows Server 2025 Security Baseline

Initiating with build 26296, we are excited to present the preview for the Windows Server 2025 Security Baseline. You can bolster your device’s or VM’s security right from the beginning by implementing a personalized security baseline, which comprises over 350 preconfigured Windows security settings that facilitate the application and enforcement of detailed security measures adhering to Microsoft’s best practices and industry standards. The content of the Windows Server 2025 Security Baseline is categorized into three sections based on the server role:

• Domain Controller (DC)
• Member Server
• Workgroup Member

Introducing Windows Server Flighting!

If you are registered for Server Flighting, you can expect to receive this new build automatically later today. For additional details, refer to Welcome to Windows Insider Flighting on Windows Server – Microsoft Community Hub.

The application is supposed to update automatically with the latest version. If this does not occur, you can manually check for updates within the app’s settings.

Known Issues

Download Windows Server Insider Preview (microsoft.com)

Flighting: The flight label might incorrectly mention Windows 11. However, rest assured that selecting it will install the Windows Server update. Please disregard the misleading label and continue with the installation. This issue is set to be resolved in an upcoming release.

WinPE – PowerShell Scripts: The optional WinPE-PowerShell component does not install PowerShell correctly within WinPE, resulting in PowerShell cmdlets failing to execute. Users reliant on PowerShell in WinPE should refrain from using this build.

If you are testing upgrades from Windows Server 2019 or 2022, we advise against using this build as intermittent upgrade failures have been documented.

Additionally, there is a known issue with the archiving of event logs using the “wevetutil al”command, which leads to the crash of the Windows Event Log service and fails the archiving process. To resolve this, the service needs to be restarted by executing “Start-Service EventLog”from an administrative command prompt.

The installation of this build is not recommended if you have the Secure Launch/DRTM code path enabled.

Download Availability

Certain downloads may not be accessible in specific countries. Please refer to Microsoft suspends new sales in Russia – Microsoft On the Issues.

• Windows Server Long-Term Servicing Channel Preview is available in ISO format in 18 languages, and in VHDX format in English only.
• Windows Server Datacenter Azure Edition Preview is available in both ISO and VHDX formats, only in English.
• Microsoft Server Languages and Optional Features Preview

Keys for Preview Builds: Keys are valid exclusively for these preview builds.

• Server Standard:MFY9F-XBN2F-TYFMP-CCV49-RMYVH
• Datacenter:2KNJJ-33Y9H-2GXGX-KMQWH-G6H67
• Azure Edition does not require a key.

Symbols: Symbols are accessible through the public symbol server – see Using the Microsoft Symbol Server.

Expiration Notice: This Windows Server Preview will expire on September 15, 2025.

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