From a51edf224e21a2a5749ba08321c276962f3ebc2c Mon Sep 17 00:00:00 2001
From: Sergey Muraviov <smurav@mail.ru>
Date: Wed, 23 Apr 2025 15:01:45 +0300
Subject: [PATCH] Fix using a null pointer in mro_hierarchy (gh-132835)

---
 Objects/typeobject.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/Objects/typeobject.c b/Objects/typeobject.c
index a720a98121dc93..0924df4def45b6 100644
--- a/Objects/typeobject.c
+++ b/Objects/typeobject.c
@@ -1652,6 +1652,9 @@ mro_hierarchy(PyTypeObject *type, PyObject *temp)
         return res;
     }
     PyObject *new_mro = lookup_tp_mro(type);
+    if (new_mro == NULL) {
+        return -1;
+    }
 
     PyObject *tuple;
     if (old_mro != NULL) {