langflow: /profile_pictures/{folder_name}/{file_name} endpoint file reading

Vulnerability

Path Traversal in GET /api/v1/files/profile_pictures/{folder_name}/{file_name}

The download_profile_picture function in src/backend/base/langflow/api/v1/files.py constructed file paths by directly concatenating the user-supplied folder_name and file_name path parameters without sanitization or boundary validation. The resulting path was passed to the filesystem without verifying it remained within the intended directory.

An unauthenticated attacker could supply traversal sequences (e.g. ../secret_key) to navigate outside the profile pictures directory and read arbitrary files on the server filesystem.

This exposed the server to:

• Sensitive file disclosure — any file readable by the application process could be retrieved
• Secret key exfiltration — the application's secret_key file, used as JWT signing material, could be read directly via ../secret_key
• Authentication bypass — with the secret_key in hand, an attacker can forge valid JWT tokens and authenticate as any user, including administrators

---

Proof of Concept

curl --path-as-is 'http://<host>:7860/api/v1/files/profile_pictures/../secret_key'

A successful response returns the raw secret key value used to sign all JWT authentication tokens in the instance.

---

Fix

The fix was applied in src/backend/base/langflow/api/v1/files.py (PR #12263).

Two layers of defense were introduced:

1. Typed path validation — the folder_name and file_name parameters were changed from plain str to ValidatedFolderName and ValidatedFileName annotated types that reject traversal characters at the FastAPI input layer.

2. Path containment check — Path.name is used to strip any directory component from the inputs before path construction, and Path.is_relative_to() verifies the resolved path remains within the allowed base directory. This replaces the previous startswith() check, which was susceptible to prefix-ambiguity bugs.

 @router.get("/profile_pictures/{folder_name}/{file_name}")
 async def download_profile_picture(
-    folder_name: str,
-    file_name: str,
+    folder_name: ValidatedFolderName,
+    file_name: ValidatedFileName,
     settings_service: Annotated[SettingsService, Depends(get_settings_service)],
 ):