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From 1194f169d7f6db3b518c40ef703135ffc4015ebe Mon Sep 17 00:00:00 2001
From: Marcelo Trylesinski <marcelotryle@gmail.com>
Date: Sun, 25 Jan 2026 10:37:09 +0100
Subject: [PATCH] Merge commit from fork
CVE: CVE-2026-24486
Upstream-Status: Backport [https://github.com/Kludex/python-multipart/commit/9433f4bbc9652bdde82bbe380984e32f8cfc89c4]
Signed-off-by: Gyorgy Sarvari <skandigraun@gmail.com>
---
python_multipart/multipart.py | 4 +++-
tests/test_file.py | 26 ++++++++++++++++++++++++++
2 files changed, 29 insertions(+), 1 deletion(-)
create mode 100644 tests/test_file.py
diff --git a/python_multipart/multipart.py b/python_multipart/multipart.py
index f26a815..7168c96 100644
--- a/python_multipart/multipart.py
+++ b/python_multipart/multipart.py
@@ -376,7 +376,9 @@ class File:
# Split the extension from the filename.
if file_name is not None:
- base, ext = os.path.splitext(file_name)
+ # Extract just the basename to avoid directory traversal
+ basename = os.path.basename(file_name)
+ base, ext = os.path.splitext(basename)
self._file_base = base
self._ext = ext
diff --git a/tests/test_file.py b/tests/test_file.py
new file mode 100644
index 0000000..4d65232
--- /dev/null
+++ b/tests/test_file.py
@@ -0,0 +1,26 @@
+from pathlib import Path
+
+from python_multipart.multipart import File
+
+
+def test_upload_dir_with_leading_slash_in_filename(tmp_path: Path):
+ upload_dir = tmp_path / "upload"
+ upload_dir.mkdir()
+
+ # When the file_name provided has a leading slash, we should only use the basename.
+ # This is to avoid directory traversal.
+ to_upload = tmp_path / "foo.txt"
+
+ file = File(
+ bytes(to_upload),
+ config={
+ "UPLOAD_DIR": bytes(upload_dir),
+ "UPLOAD_KEEP_FILENAME": True,
+ "UPLOAD_KEEP_EXTENSIONS": True,
+ "MAX_MEMORY_FILE_SIZE": 10,
+ },
+ )
+ file.write(b"123456789012")
+ assert not file.in_memory
+ assert Path(upload_dir / "foo.txt").exists()
+ assert Path(upload_dir / "foo.txt").read_bytes() == b"123456789012"
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