When row-level security is used in a tabular instance of SQL Server 2014 Analysis Services (SSAS 2014), queries cannot be canceled in a timely manner. If you try to commit any data change, it will be blocked. Additionally, it may prevent the other users from connecting to the tabular instance.
The issue was first fixed in the following cumulative update of SQL Server:
Recommendation: Install the latest cumulative update for SQL Server
Each new cumulative update for SQL Server contains all the hotfixes and all the security fixes that were included with the previous cumulative update. We recommend that you download and install the latest cumulative updates for SQL Server: