Windows 11 build 25951 outs in Canary Channel

• Windows 11 build 25951 arrives for testers in the Canary Channel.
• This flight rolls out fixes for various system components.

Windows 11 build 25951 is now available for devices enrolled in the Canary Channel of the Windows Insider Program with some additional fixes, changes, and improvements.

Build 25951 for Windows 11, according to the official changes, the SMB client now supports blocking NTLM for remote outbound connections, and the SMB server now supports controlling which SMB 2 and 3 dialects it will negotiate.

In the SMB client, this changes legacy behavior, where Windows SPNEGO would negotiate Kerberos, NTLM, and other mechanisms with the destination server to decide on a supported security package. NTLM, in this case, refers to all versions of the LAN Manager security package: LM, NTLM, and NTLMv2.

Using this new option, administrators can intentionally block the operating system from offering NTLM through SMB, adding a new level of protection for enterprises without a requirement to entirely disable NTLM usage.

In the SMB server, this changes legacy behavior, where SMB always negotiated the highest matched server dialect from SMB 2.0.2 to 3.1.1 clients. The support for controlling SMB client dialects has been available since Windows 10, but not server dialects.

Using this new option, administrators can remove older SMB protocols from usage in the organization, blocking older, less secure, and less capable Windows devices and third parties from connecting. Finally, you can configure these settings with Group Policy and PowerShell. 

Also, the development team made changes to the network flyout on the Lock screen to better match the UI of the network flyout from quick settings in the System Tray on the Taskbar.

As part of the known issues, the company notes that some popular games may not work correctly in this rollout, and it’s investigating reports that the print queue is no longer accessible.

Installing builds

To download and install the Windows 11 build 25951, you must enroll your device in the Canary Channel through the “Windows Insider Program” settings from the “Update & Security” section. Once you enroll the computer in the program, you can download the build from the “Windows Update” settings by clicking the “Check for Updates” button.