CVE-2023-26145: Improper Control of Generation of Code ('Code Injection') (CWE-94)
value: This affects versions of the package pydash before 6.0.0. A number of pydash methods such as pydash.objects.invoke() and pydash.collections.invoke_map() accept dotted paths (Deep Path Strings) to target a nested Python object, relative to the original source object. These paths can be used to target internal class attributes and dict items, to retrieve, modify or invoke nested Python objects.**Note:**The pydash.objects.invoke() method is vulnerable to Command Injection when the following prerequisites are satisfied:1) The source object (argument 1) is not a built-in object such as list/dict (otherwise, the __init__.__globals__ path is not accessible)2) The attacker has control over argument 2 (the path string) and argument 3 (the argument to pass to the invoked method)The pydash.collections.invoke_map() method is also vulnerable, but is harder to exploit as the attacker does not have direct control over the argument to be passed to the invoked function.
CWE description: The product constructs all or part of a code segment using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the syntax or behavior of the intended code segment.
CVSS v3 base score: 8.1
Published: 2023-09-28T05:15Z
Repository: https://github.com/dgilland/pydash
Language: Python
Files changed: src/pydash/helpers.py, tests/test_objects.py
Commit date: 2023-01-28 20:30:52 -0500
Commit message: fix: don't allow object paths that reference dunder-method attributes for functions like get()

Diff: diff --git a/src/pydash/helpers.py b/src/pydash/helpers.py
index 0467c9c..a6033f9 100644
--- a/src/pydash/helpers.py
+++ b/src/pydash/helpers.py
@@ -176,18 +176,26 @@ def _base_get_item(obj, key, default=UNSET):
 
 
 def _base_get_object(obj, key, default=UNSET):
     value = _base_get_item(obj, key, default=UNSET)
     if value is UNSET:
+        _raise_if_restricted_key(key)
         value = default
         try:
             value = getattr(obj, key)
         except Exception:
             pass
     return value
 
 
+def _raise_if_restricted_key(key):
+    # Prevent access to dunder-methods since this could expose access to globals through leaky
+    # attributes such as obj.__init__.__globals__.
+    if len(key) > 4 and key.isascii() and key.startswith("__") and key.endswith("__"):
+        raise KeyError(f"access to restricted key {key!r} is not allowed")
+
+
 def base_set(obj, key, value, allow_override=True):
     """
     Set an object's `key` to `value`. If `obj` is a ``list`` and the `key` is the next available
     index position, append to list; otherwise, pad the list of ``None`` and then append to the list.
 
@@ -211,10 +219,11 @@ def base_set(obj, key, value, allow_override=True):
                 # Pad list object with None values up to the index key so we can append the value
                 # into the key index.
                 obj[:] = (obj + [None] * key)[:key]
             obj.append(value)
     elif (allow_override or not hasattr(obj, key)) and obj is not None:
+        _raise_if_restricted_key(key)
         setattr(obj, key, value)
 
     return obj
 
 
diff --git a/tests/test_objects.py b/tests/test_objects.py
index ae239e7..a21d75d 100644
--- a/tests/test_objects.py
+++ b/tests/test_objects.py
@@ -378,10 +378,34 @@ def test_get__should_not_populate_defaultdict():
     data = defaultdict(list)
     _.get(data, "a")
     assert data == {}
 
 
+@parametrize(
+    "obj,path",
+    [
+        (helpers.Object(), "__init__"),
+        (helpers.Object(subobj=helpers.Object()), "subobj.__init__"),
+        (namedtuple("a", ["a"])(a=1), "__len__"),
+    ],
+)
+def test_get__raises_for_objects_when_path_restricted(obj, path):
+    with pytest.raises(KeyError, match="access to restricted key"):
+        _.get(obj, path)
+
+
+@parametrize(
+    "obj,path",
+    [
+        ({}, "__init__"),
+        ([], "__contains__"),
+    ],
+)
+def test_get__does_not_raise_for_dict_or_list_when_path_restricted(obj, path):
+    assert _.get(obj, path) is None
+
+
 @parametrize(
     "case,expected",
     [
         (({"a": 1, "b": 2, "c": 3}, "b"), True),
         (([1, 2, 3], 0), True),

Fixed code:         _raise_if_restricted_key(key)
def _raise_if_restricted_key(key):
    # Prevent access to dunder-methods since this could expose access to globals through leaky
    # attributes such as obj.__init__.__globals__.
    if len(key) > 4 and key.isascii() and key.startswith("__") and key.endswith("__"):
        raise KeyError(f"access to restricted key {key!r} is not allowed")


        _raise_if_restricted_key(key)
@parametrize(
    "obj,path",
    [
        (helpers.Object(), "__init__"),
        (helpers.Object(subobj=helpers.Object()), "subobj.__init__"),
        (namedtuple("a", ["a"])(a=1), "__len__"),
    ],
)
def test_get__raises_for_objects_when_path_restricted(obj, path):
    with pytest.raises(KeyError, match="access to restricted key"):
        _.get(obj, path)


@parametrize(
    "obj,path",
    [
        ({}, "__init__"),
        ([], "__contains__"),
    ],
)
def test_get__does_not_raise_for_dict_or_list_when_path_restricted(obj, path):
    assert _.get(obj, path) is None