Because any valid SQL Server or MSDE user can create a temporary stored procedure, this vulnerability would enable a malicious user to execute any stored procedure owned by the dbo user. Stored procedures are available for managing SQL Server and displaying information about databases and users. A temporary stored procedure is one that exists only during a single user session. In most cases, permission checking occurs as one would expect - before SQL Server will allow a user to execute a stored procedure, it verifies that he has permission to do so. This could give a malicious user a way to execute a stored procedure that he otherwise wouldn't be able to.
Any object created by any member of the sysadmin fixed server role belongs to dbo automatically.
Suppose that the dbo user within database ABC, of SQL Server XYZ, has written several stored procedures that let him perform maintenance on the server. Now suppose that Joeuser has an account on the same server and was given access to the ABC database. By design, Joeuser's temporary stored procedure should not be able to run the administrator's procedure, but the vulnerability would enable it to do so. Only databases that are owned by sa login account are affected by this vulnerability. It is imperative that the sa login account be used only for specific SQL Server administrative tasks.