CVE-2021-42340 - Missing Release of Resource after Effective Lifetime

The following code attempts to process a file by reading it in line by line until the end has been reached.

               
}
}
processLine(line);

The problem with the above code is that it never closes the file handle it opens. The Finalize() method for BufferReader eventually calls Close(), but there is no guarantee as to how long it will take before the Finalize() method is invoked. In fact, there is no guarantee that Finalize() will ever be invoked. In a busy environment, this can result in the VM using up all of its available file handles.

The following code attempts to open a new connection to a database, process the results returned by the database, and close the allocated SqlConnection object.

               
conn.Connection.Close();

The problem with the above code is that if an exception occurs while executing the SQL or processing the results, the SqlConnection object is not closed. If this happens often enough, the database will run out of available cursors and not be able to execute any more SQL queries.

The following method never closes the file handle it opens. The Finalize() method for StreamReader eventually calls Close(), but there is no guarantee as to how long it will take before the Finalize() method is invoked. In fact, there is no guarantee that Finalize() will ever be invoked. In a busy environment, this can result in the VM using up all of its available file handles.

               
}
}
processLine(line);

This code attempts to open a connection to a database and catches any exceptions that may occur.

               
}
Connection con = DriverManager.getConnection(some_connection_string);
log( e );

If an exception occurs after establishing the database connection and before the same connection closes, the pool of database connections may become exhausted. If the number of available connections is exceeded, other users cannot access this resource, effectively denying access to the application.

Under normal conditions the following C# code executes a database query, processes the results returned by the database, and closes the allocated SqlConnection object. But if an exception occurs while executing the SQL or processing the results, the SqlConnection object is not closed. If this happens often enough, the database will run out of available cursors and not be able to execute any more SQL queries.

               
...

The following C function does not close the file handle it opens if an error occurs. If the process is long-lived, the process can run out of file handles.

               
}

                     
return DECODE_SUCCESS;
return DECODE_FAIL;

                           
}
}
return DECODE_FAIL;
decodeBlock(buf);