Oracle Database open cursors 18446744073709551612

Oracle version (11.2.0.4.0) shows session opens 18446744073709551612 cursors. What happen?

SQL> show parameter curso

NAME                                 TYPE        VALUE

------------------------------------ ----------- ------------------------------

cursor_bind_capture_destination      string      memory+disk

cursor_sharing                       string      EXACT

cursor_space_for_time                boolean     FALSE

open_cursors                         integer     400

session_cached_cursors               integer     50

SQL> SELECT  max(a.value) as highest_open_cur, p.value as max_open_cur FROM v$sesstat a, v$statname b, v$parameter p WHERE  a.statistic# = b.statistic#  and b.name = 'opened cursors current' and p.name= 'open_cursors' group by p.value;

      HIGHEST_OPEN_CUR   MAX_OPEN_CUR

---------------------- ------------------

  18446744073709551612 400