CU 4 was released yesterday, and as in previous versions, contains the hotfixes that have been developed since the release of SP2. Like with cumulative update 3, this one is also multilanguage and is available through writing a request to Microsoft Online Customer Services at http://go.microsoft.com/?linkid=6294451. To install cumulative update package 4 for SQL Server 2005 Service Pack 2, you need to enable the SMO and the SQL-DMO stored procedures.
The cumulative update is also known as build 3200. For further detail, please see the knowledge base article.