Issue #18560: Fix potential NULL pointer dereference in sum()

Misc/NEWS

@@ -12,6 +12,8 @@ What's New in Python 3.3.3 release candidate 1?
 Core and Builtins
 -----------------
 
+- Issue #18560: Fix potential NULL pointer dereference in sum().
+
 - Issue #15905: Fix theoretical buffer overflow in handling of sys.argv[0],
   prefix and exec_prefix if the operation system does not obey MAXPATHLEN.
 

Python/bltinmodule.c

@@ -2009,6 +2009,11 @@ builtin_sum(PyObject *self, PyObject *args)
             }
             /* Either overflowed or is not an int. Restore real objects and process normally */
             result = PyLong_FromLong(i_result);
+            if (result == NULL) {
+                Py_DECREF(item);
+                Py_DECREF(iter);
+                return NULL;
+            }
             temp = PyNumber_Add(result, item);
             Py_DECREF(result);
             Py_DECREF(item);