From 9a47a009d645a8ce0c613640494e10958ad19bce Mon Sep 17 00:00:00 2001
From: Buffett Liu <jengliu@linkedin.com>
Date: Mon, 13 Jul 2026 14:26:17 -0700
Subject: [PATCH] Fixing path traversal/arbitrary out-of-directory file read
 via sharded-checkpoint

---
 src/diffusers/utils/hub_utils.py |  7 ++++++
 tests/others/test_hub_utils.py   | 41 +++++++++++++++++++++++++++++++-
 2 files changed, 47 insertions(+), 1 deletion(-)

diff --git a/src/diffusers/utils/hub_utils.py b/src/diffusers/utils/hub_utils.py
index b5eb9ab2e17f..561d27392fad 100644
--- a/src/diffusers/utils/hub_utils.py
+++ b/src/diffusers/utils/hub_utils.py
@@ -392,6 +392,13 @@ def _get_checkpoint_shard_files(
             index = json.loads(f.read())
 
     original_shard_filenames = sorted(set(index["weight_map"].values()))
+    for shard_filename in original_shard_filenames:
+        if os.path.basename(shard_filename) != shard_filename:
+            raise ValueError(
+                f"The shard filename {shard_filename!r} in the checkpoint index contains a path separator or a "
+                "parent-directory reference, which is not allowed. Shard filenames must be plain filenames located "
+                "in the model directory."
+            )
     sharded_metadata = index["metadata"]
     sharded_metadata["all_checkpoint_keys"] = list(index["weight_map"].keys())
     sharded_metadata["weight_map"] = index["weight_map"].copy()
diff --git a/tests/others/test_hub_utils.py b/tests/others/test_hub_utils.py
index de6ab198e501..c897afd26db9 100644
--- a/tests/others/test_hub_utils.py
+++ b/tests/others/test_hub_utils.py
@@ -12,11 +12,17 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+import json
+import os
 import unittest
 from pathlib import Path
 from tempfile import TemporaryDirectory
 
-from diffusers.utils.hub_utils import load_or_create_model_card, populate_model_card
+from diffusers.utils.hub_utils import (
+    _get_checkpoint_shard_files,
+    load_or_create_model_card,
+    populate_model_card,
+)
 
 
 class CreateModelCardTest(unittest.TestCase):
@@ -27,3 +33,36 @@ def test_generate_model_card_with_library_name(self):
             model_card = load_or_create_model_card(file_path)
             populate_model_card(model_card)
             assert model_card.data.library_name == "foo"
+
+
+class GetCheckpointShardFilesTest(unittest.TestCase):
+    def _write_index(self, model_dir, shard_filename):
+        index = {"metadata": {"total_size": 1}, "weight_map": {"w": shard_filename}}
+        index_filename = os.path.join(model_dir, "diffusion_pytorch_model.safetensors.index.json")
+        with open(index_filename, "w") as f:
+            json.dump(index, f)
+        return index_filename
+
+    def test_rejects_parent_directory_traversal(self):
+        with TemporaryDirectory() as tmpdir:
+            model_dir = os.path.join(tmpdir, "model")
+            os.makedirs(model_dir)
+            index_filename = self._write_index(model_dir, "../secret/SECRET.safetensors")
+            with self.assertRaises(ValueError):
+                _get_checkpoint_shard_files(model_dir, index_filename)
+
+    def test_rejects_absolute_path(self):
+        with TemporaryDirectory() as tmpdir:
+            model_dir = os.path.join(tmpdir, "model")
+            os.makedirs(model_dir)
+            index_filename = self._write_index(model_dir, os.path.join(tmpdir, "secret", "SECRET.safetensors"))
+            with self.assertRaises(ValueError):
+                _get_checkpoint_shard_files(model_dir, index_filename)
+
+    def test_rejects_subdirectory_component(self):
+        with TemporaryDirectory() as tmpdir:
+            model_dir = os.path.join(tmpdir, "model")
+            os.makedirs(model_dir)
+            index_filename = self._write_index(model_dir, "sub/shard.safetensors")
+            with self.assertRaises(ValueError):
+                _get_checkpoint_shard_files(model_dir, index_filename)