Hello,

I encounter a quite similar issue with python 3.4.0 and cx_Oracle. It segfault from time to time (hard to reproduce) on visit_decref at Modules/gcmodule.c:373.
There were no issue with python 2.7. I did not test with 3.3.

With gdb i got the following stacktrace :
(gdb) info threads
  Id   Target Id         Frame 
* 1    Thread 0x7ffff7fc6740 (LWP 7415) "python3" visit_decref (op=0xb00000000, data=data@entry=0x0) at Modules/gcmodule.c:373
(gdb) backtrace 
#0  visit_decref (op=0xb00000000, data=data@entry=0x0) at Modules/gcmodule.c:373
#1  0x00000000004318da in BaseException_traverse (self=0x7ffff1624888, visit=0x504660 <visit_decref>, arg=0x0) at Objects/exceptions.c:97
#2  0x0000000000504925 in subtract_refs (containers=<optimized out>) at Modules/gcmodule.c:398
#3  collect (generation=generation@entry=0, n_collected=n_collected@entry=0x7fffffffbd60, n_uncollectable=n_uncollectable@entry=0x7fffffffbd68, nofail=nofail@entry=0) at Modules/gcmodule.c:957
#4  0x0000000000505573 in collect_with_callback (generation=0) at Modules/gcmodule.c:1128
#5  collect_generations () at Modules/gcmodule.c:1151
#6  0x0000000000505cd1 in _PyObject_GC_Malloc (basicsize=<optimized out>) at Modules/gcmodule.c:1726
#7  _PyObject_GC_Malloc (basicsize=<optimized out>) at Modules/gcmodule.c:1743
#8  _PyObject_GC_NewVar (tp=tp@entry=0x810400 <PyTuple_Type>, nitems=nitems@entry=11) at Modules/gcmodule.c:1753
#9  0x000000000046470c in PyTuple_New (size=11) at Objects/tupleobject.c:104
#10 0x0000000000464e05 in PyTuple_New (size=size@entry=11) at Objects/tupleobject.c:122
#11 0x00007ffff582e881 in Cursor_CreateRow (self=self@entry=0x7ffff1603290) at Cursor.c:1095
#12 0x00007ffff582f18f in Cursor_MultiFetch (self=0x7ffff1603290, rowLimit=0) at Cursor.c:1883
#13 0x00000000004c4aa7 in call_function (oparg=<optimized out>, pp_stack=0x7fffffffbfb0) at Python/ceval.c:4210
#14 PyEval_EvalFrameEx (f=f@entry=0xab5208, throwflag=throwflag@entry=0) at Python/ceval.c:2829
#15 0x00000000004be47b in PyEval_EvalCodeEx (_co=<optimized out>, globals=<optimized out>, locals=locals@entry=0x0, args=<optimized out>, argcount=argcount@entry=3, kws=0x7ffff11c3ad8, kwcount=0, defs=0x7ffff5a635a0, defcount=1, kwdefs=0x0, 
    closure=0x0) at Python/ceval.c:3578
#16 0x00000000004c3d91 in fast_function (nk=<optimized out>, na=3, n=<optimized out>, pp_stack=0x7fffffffc240, func=0x7ffff1e98b70) at Python/ceval.c:4334
#17 call_function (oparg=<optimized out>, pp_stack=0x7fffffffc240) at Python/ceval.c:4252
#18 PyEval_EvalFrameEx (f=f@entry=0x7ffff11c3930, throwflag=throwflag@entry=0) at Python/ceval.c:2829
#19 0x00000000004be47b in PyEval_EvalCodeEx (_co=<optimized out>, globals=<optimized out>, locals=locals@entry=0x0, args=<optimized out>, argcount=argcount@entry=2, kws=0xbf7610, kwcount=1, defs=0x7ffff1eb14c0, defcount=1, kwdefs=0x0, 
    closure=0x0) at Python/ceval.c:3578
#20 0x00000000004c3d91 in fast_function (nk=<optimized out>, na=2, n=<optimized out>, pp_stack=0x7fffffffc4d0, func=0x7ffff160b510) at Python/ceval.c:4334
#21 call_function (oparg=<optimized out>, pp_stack=0x7fffffffc4d0) at Python/ceval.c:4252
#22 PyEval_EvalFrameEx (f=<optimized out>, throwflag=throwflag@entry=0) at Python/ceval.c:2829
#23 0x00000000004c5e85 in fast_function (nk=<optimized out>, na=2, n=2, pp_stack=0x7fffffffc6b0, func=0x7ffff1634d08) at Python/ceval.c:4324
#24 call_function (oparg=<optimized out>, pp_stack=0x7fffffffc6b0) at Python/ceval.c:4252
#25 PyEval_EvalFrameEx (f=<optimized out>, throwflag=throwflag@entry=0) at Python/ceval.c:2829
#26 0x00000000004c5e85 in fast_function (nk=<optimized out>, na=2, n=2, pp_stack=0x7fffffffc890, func=0x7ffff2513730) at Python/ceval.c:4324
#27 call_function (oparg=<optimized out>, pp_stack=0x7fffffffc890) at Python/ceval.c:4252
#28 PyEval_EvalFrameEx (f=<optimized out>, throwflag=throwflag@entry=0) at Python/ceval.c:2829
#29 0x00000000004c5e85 in fast_function (nk=<optimized out>, na=2, n=2, pp_stack=0x7fffffffca70, func=0x7ffff1633378) at Python/ceval.c:4324
#30 call_function (oparg=<optimized out>, pp_stack=0x7fffffffca70) at Python/ceval.c:4252
---Type <return> to continue, or q <return> to quit---
#31 PyEval_EvalFrameEx (f=<optimized out>, throwflag=throwflag@entry=0) at Python/ceval.c:2829
#32 0x00000000004c5e85 in fast_function (nk=<optimized out>, na=2, n=2, pp_stack=0x7fffffffcc50, func=0x7ffff1635d90) at Python/ceval.c:4324
#33 call_function (oparg=<optimized out>, pp_stack=0x7fffffffcc50) at Python/ceval.c:4252
#34 PyEval_EvalFrameEx (f=<optimized out>, throwflag=throwflag@entry=0) at Python/ceval.c:2829
#35 0x00000000004c5e85 in fast_function (nk=<optimized out>, na=2, n=2, pp_stack=0x7fffffffce30, func=0x7ffff2513730) at Python/ceval.c:4324
#36 call_function (oparg=<optimized out>, pp_stack=0x7fffffffce30) at Python/ceval.c:4252
#37 PyEval_EvalFrameEx (f=<optimized out>, throwflag=throwflag@entry=0) at Python/ceval.c:2829
#38 0x00000000004c5e85 in fast_function (nk=<optimized out>, na=2, n=2, pp_stack=0x7fffffffd010, func=0x7ffff1633378) at Python/ceval.c:4324
#39 call_function (oparg=<optimized out>, pp_stack=0x7fffffffd010) at Python/ceval.c:4252
#40 PyEval_EvalFrameEx (f=f@entry=0xab9478, throwflag=throwflag@entry=0) at Python/ceval.c:2829
#41 0x00000000004be47b in PyEval_EvalCodeEx (_co=<optimized out>, globals=<optimized out>, locals=locals@entry=0x0, args=<optimized out>, argcount=argcount@entry=1, kws=0xab9380, kwcount=0, defs=0x7ffff2504b88, defcount=1, kwdefs=0x0, 
    closure=0x0) at Python/ceval.c:3578
#42 0x00000000004c3d91 in fast_function (nk=<optimized out>, na=1, n=<optimized out>, pp_stack=0x7fffffffd2a0, func=0x7ffff2513400) at Python/ceval.c:4334
#43 call_function (oparg=<optimized out>, pp_stack=0x7fffffffd2a0) at Python/ceval.c:4252
#44 PyEval_EvalFrameEx (f=<optimized out>, throwflag=throwflag@entry=0) at Python/ceval.c:2829
#45 0x00000000004c5e85 in fast_function (nk=<optimized out>, na=1, n=1, pp_stack=0x7fffffffd480, func=0x7ffff16331e0) at Python/ceval.c:4324
#46 call_function (oparg=<optimized out>, pp_stack=0x7fffffffd480) at Python/ceval.c:4252
#47 PyEval_EvalFrameEx (f=<optimized out>, throwflag=throwflag@entry=0) at Python/ceval.c:2829
#48 0x00000000004c5e85 in fast_function (nk=<optimized out>, na=0, n=0, pp_stack=0x7fffffffd660, func=0x7ffff6ed4d08) at Python/ceval.c:4324
#49 call_function (oparg=<optimized out>, pp_stack=0x7fffffffd660) at Python/ceval.c:4252
#50 PyEval_EvalFrameEx (f=f@entry=0x7ffff7eceaf8, throwflag=throwflag@entry=0) at Python/ceval.c:2829
#51 0x00000000004be47b in PyEval_EvalCodeEx (_co=_co@entry=0x7ffff6ed14b0, globals=globals@entry=0x7ffff7ef1388, locals=locals@entry=0x7ffff7ef1388, args=args@entry=0x0, argcount=argcount@entry=0, kws=kws@entry=0x0, kwcount=kwcount@entry=0, 
    defs=defs@entry=0x0, defcount=defcount@entry=0, kwdefs=kwdefs@entry=0x0, closure=closure@entry=0x0) at Python/ceval.c:3578
#52 0x00000000004be54b in PyEval_EvalCode (co=co@entry=0x7ffff6ed14b0, globals=globals@entry=0x7ffff7ef1388, locals=locals@entry=0x7ffff7ef1388) at Python/ceval.c:773
#53 0x00000000004ed844 in run_mod (arena=0x8fea30, flags=0x7fffffffd910, locals=0x7ffff7ef1388, globals=0x7ffff7ef1388, filename=0x7ffff7ea7a78, mod=0x97c090) at Python/pythonrun.c:2175
#54 PyRun_InteractiveOneObject (fp=fp@entry=0x7ffff74b6340 <_IO_2_1_stdin_>, filename=filename@entry=0x7ffff7ea7a78, flags=flags@entry=0x7fffffffd910) at Python/pythonrun.c:1441
#55 0x00000000004edb7e in PyRun_InteractiveLoopFlags (fp=fp@entry=0x7ffff74b6340 <_IO_2_1_stdin_>, filename_str=filename_str@entry=0x580d63 "<stdin>", flags=flags@entry=0x7fffffffd910) at Python/pythonrun.c:1320
#56 0x00000000004edcd6 in PyRun_AnyFileExFlags (fp=fp@entry=0x7ffff74b6340 <_IO_2_1_stdin_>, filename=<optimized out>, closeit=0, flags=flags@entry=0x7fffffffd910) at Python/pythonrun.c:1282
#57 0x000000000041e243 in run_file (p_cf=0x7fffffffd910, filename=0x0, fp=0x7ffff74b6340 <_IO_2_1_stdin_>) at Modules/main.c:319
#58 Py_Main (argc=argc@entry=1, argv=argv@entry=0x872010) at Modules/main.c:751
#59 0x000000000041aacc in main (argc=1, argv=<optimized out>) at ./Modules/python.c:69
(gdb) 


Regards