When you use the Microsoft ODBC Driver 11 for SQL Server in a multithreaded application, a connection attempt (SQLDriverConect/SQLConnect) results in an access violation.
This issue occurs because of a race condition that is caused by an oversight during initialization. When two or more threads try to create connections, the issue occurs.
To work around this issue, use an application that can establish the first connection in a single thread. If the first connection is established in a single thread, the SQL Server Native Client 11 driver (that is, the earlier ODBC driver version) won't be used to make the first connection attempt. This avoids the issue.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.