⚠️ SECURITY-#29: Sanitize attachment filenames against path traversal

email_profile/parser.py

@@ -213,11 +213,15 @@ def parse_rfc822(raw_message: bytes) -> ParsedBody:
             if not filename:
                 continue
 
+            safe_name = Path(_decode_header(filename).replace("\\", "/")).name
+            if not safe_name or safe_name in (".", ".."):
+                continue
+
             payload = part.get_payload(decode=True) or b""
 
             body.attachments.append(
                 Attachment(
-                    file_name=_decode_header(filename),
+                    file_name=safe_name,
                     content_type=content_type,
                     content=(
                         payload

tests/test_parser.py

@@ -42,6 +42,32 @@ def test_content(self):
         )
 
 
+class TestAttachmentPathTraversal(TestCase):
+    def _msg(self, filename: str) -> bytes:
+        return (
+            b"From: a@x\r\nTo: b@x\r\nSubject: t\r\n"
+            b'Content-Type: multipart/mixed; boundary="B"\r\n\r\n'
+            b"--B\r\nContent-Type: text/plain\r\n\r\nbody\r\n"
+            b"--B\r\nContent-Disposition: attachment; "
+            b'filename="' + filename.encode() + b'"\r\n\r\n'
+            b"payload\r\n--B--\r\n"
+        )
+
+    def test_unix_traversal_stripped(self):
+        atts = parse_rfc822(self._msg("../../etc/passwd")).attachments
+        self.assertEqual(len(atts), 1)
+        self.assertEqual(atts[0].file_name, "passwd")
+
+    def test_windows_traversal_stripped(self):
+        atts = parse_rfc822(
+            self._msg("..\\\\..\\\\windows\\\\evil.exe")
+        ).attachments
+        self.assertEqual(atts[0].file_name, "evil.exe")
+
+    def test_pure_traversal_dropped(self):
+        self.assertEqual(parse_rfc822(self._msg("../..")).attachments, [])
+
+
 class TestNamedHeaders(TestCase):
     def test_named_headers_extracted(self):
         raw = (