Windows Home Server 2011 Update Rollup 4 has been released and is available from Windows Update. You can read about the details in Microsoft Support Knowledgebase 2757011.
In addition to the server-side update, a client-side update has been released as well. This update is documented in KB
2757014. The client-side package will be downloaded to the server along with the Update rollup. User does not have to go to the Windows Update website to obtain the package separately.
More Information
2757011 Update Rollup 4 for Windows Home Server 2011 is available
http://support.microsoft.com/kb/2757011
2757014 Client-side update package is available for Update Rollup 4 for Windows Small Business Server 2011 Essentials, Windows Home Server 2011, and Windows Storage Server 2008
R2 Essentials
http://support.microsoft.com/kb/2757014
This post is "AS IS" and confers no rights. Ning Kuang[MSFT] Windows Server Program Manager