Windows 11: Important security update for release preview

In addition to the regular updates for September Patch Day, Microsoft has also released a security update for the preview version of Windows 11. This update fixes the reported security vulnerabilities for all RP testers. According to the report, KB5017321 is now being distributed as a security-related update for Windows 11 Version 22H2. The new build number is 22621.521. The update is cumulative and includes all improvements from optional update KB5016695 released in August.

According to the first reports, problems with the Windows Common Log File System (CLFS), Windows TCP/IP, and the Windows Kernel in particular have been fixed. A total of more than 60 security gaps were fixed again on patch day. There was also a zero-day vulnerability. A list of the security-relevant changes can be found in the Microsoft Security Update Guide.

Improved SMB compression

In addition to the security-related changes, there are also new functions. These were released to all Windows users on September Patch Day. This is a new, improved SMB compression that fully compresses files regardless of their original size. In addition, Microsoft Defender for Endpoint has been improved so that it now better detects and intercepts ransomware and advanced attacks.

The Windows Insider Team has not released any further details about KB5017321. The security update is available to users of the Release Preview channel. This patch is also available for retail tests. All other Windows Insiders, i.e. users who have selected the beta or dev channel, will not be offered this update.