CVE-2013-2132 (published 2013-08-15T17:55Z)

bson/_cbsonmodule.c in the mongo-python-driver (aka. pymongo) before 2.5.2, as used in MongoDB, allows context-dependent attackers to cause a denial of service (NULL pointer dereference and crash) via vectors related to decoding of an "invalid DBRef."

Severity: MEDIUM
CVSS v2 base score: 4.3 (AV:N/AC:M/Au:N/C:N/I:N/A:P)

Weakness information:
cwe_id: NVD-CWE-Other
cwe_name: Other
description: NVD is only using a subset of CWE for mapping instead of the entire CWE, and the weakness type is not covered by that subset.
extended_description: Insufficient Information

Fix information:
repo_url: https://github.com/mongodb/mongo-python-driver
commit_details: repo_url: https://github.com/mongodb/mongo-python-driver
author: A. Jesse Jiryu Davis
author_date: 2013-05-31 10:17:46-04:00
msg: Fix null pointer when decoding invalid DBRef PYTHON-532
repository: repo_url: https://github.com/mongodb/mongo-python-driver
repo_name: mongodb/mongo-python-driver
description: PyMongo - the Official MongoDB Python driver
repo_language: Python
owner: mongodb
file_changes: filename: __init__.py
change_type: ModificationType.MODIFY
diff: @@ -150,7 +150,7 @@ def _get_object(data, position, as_class, tz_aware, uuid_subtype):
     object = _elements_to_dict(encoded, as_class, tz_aware, uuid_subtype)
     position += obj_size
     if "$ref" in object:
-        return (DBRef(object.pop("$ref"), object.pop("$id"),
+        return (DBRef(object.pop("$ref"), object.pop("$id", None),
                       object.pop("$db", None), object), position)
     return object, position
 

programming_language: Python
filename: _cbsonmodule.c
change_type: ModificationType.MODIFY
diff: @@ -1202,8 +1202,14 @@ static PyObject* get_value(PyObject* self, const char* buffer, int* position,
 
                 Py_INCREF(collection);
                 PyDict_DelItemString(value, "$ref");
-                Py_INCREF(id);
-                PyDict_DelItemString(value, "$id");
+
+                if (id == NULL) {
+                    id = Py_None;
+                    Py_INCREF(id);
+                } else {
+                    Py_INCREF(id);
+                    PyDict_DelItemString(value, "$id");
+                }
 
                 if (database == NULL) {
                     database = Py_None;

programming_language: C
filename: test_collection.py
change_type: ModificationType.MODIFY
diff: @@ -30,6 +30,7 @@ sys.path[0:0] = [""]
 
 from bson.binary import Binary, UUIDLegacy, OLD_UUID_SUBTYPE, UUID_SUBTYPE
 from bson.code import Code
+from bson.dbref import DBRef
 from bson.objectid import ObjectId
 from bson.py3compat import b
 from bson.son import SON
@@ -1675,6 +1676,31 @@ class TestCollection(unittest.TestCase):
         self.assertRaises(InvalidDocument, c.save, {"x": c})
         warnings.simplefilter("default")
 
+    def test_bad_dbref(self):
+        c = self.db.test
+        c.drop()
+
+        # Incomplete DBRefs.
+        self.assertRaises(
+            InvalidDocument,
+            c.insert, {'ref': {'$ref': 'collection'}})
+
+        self.assertRaises(
+            InvalidDocument,
+            c.insert, {'ref': {'$id': ObjectId()}})
+
+        ref_only = {'ref': {'$ref': 'collection'}}
+        id_only = {'ref': {'$id': ObjectId()}}
+
+        # Force insert of ref without $id.
+        c.insert(ref_only, check_keys=False)
+        self.assertEqual(DBRef('collection', id=None), c.find_one()['ref'])
+        c.drop()
+
+        # DBRef without $ref is decoded as normal subdocument.
+        c.insert(id_only, check_keys=False)
+        self.assertEqual(id_only, c.find_one())
+
     def test_as_class(self):
         c = self.db.test
         c.drop()

programming_language: Python