In some cases type->tp_mro can be NULL and the new_mro variable can get a null value from the lookup_tp_mro call in the mro_hierarchy function.

In this case, there may be problems with calling the Py_NewRef and the Py_DECREF functions.

Linked PRs

• gh-132835: Fix using a null pointer in mro_hierarchy #132836
• gh-132835: Add defensive NULL checks in mro resolution #134763