Update Rollup 2 for Exchange 2007 has just been released.  The update is available from the following location:

http://www.microsoft.com/downloads/details.aspx?FamilyId=356874EF-C9C0-4842-99F0-E449E9940358&displaylang=en

The associated article is as follows:  http://support.microsoft.com/?kbid=935490

The update includes the fixes for the issues that are described in Microsoft security bulletin MS07-026 (http://www.microsoft.com/technet/security/bulletin/ms07-026.mspx)