GHSA-qrpv-q767-xqq2: Langflow: IDOR Vulnerability in `/api/v1/responses` Endpoint Allows Authenticated Attackers to Access Another User's Flow

Summary Insecure Direct Object Reference (IDOR) vulnerability in /api/v1/responses endpoint allows an authenticated attacker to execute any flow belonging to another user by specifying the victim's flow ID in the request. Details The vulnerability exists in the get_flow_by_id_or_endpoint_name helper function in src/backend/base/langflow/helpers/flow.py (lines 399-414). When a flow is accessed via UUID (flow_id), the function queries the database directly without verifying if the authenticated user owns that flow: src/backend/base/langflow/helpers/flow.py:399-414 async def get_flow_by_id_or_endpoint_name(flow_id_or_name: str, user_id: str | UUID | None = None) -> FlowRead: async with session_scope() as session: try: flow_id = UUID(flow_id_or_name) When using UUID, query directly WITHOUT checking user_id flow = await session.get(Flow, flow_id) # ❌ No user_id check! except ValueError: endpoint_name = flow_id_or_name stmt = select(Flow).where(Flow.endpoint_name == endpoint_name) Only when using endpoint_name is user_id checked if user_id: stmt = stmt.where(Flow.user_id == uuid_user_id) This function is used by the /api/v1/responses endpoint (defined in src/backend/base/langflow/api/v1/openai_responses.py:589). PoC (Proof of Concept) Attacker (user A) with API_KEY_A tries to execute victim (user B)'s flow curl -X POST "http://localhost:7860/api/v1/responses" \ -H "x-api-key: sk-ATTACKER_API_KEY" \ -H "Content-Type: application/json" \ -d '{ "model": "VICTIM_FLOW_ID", "input_value": "test", "stream": false }' Returns 200 and executes the victim's flow Impact Any authenticated user can: 1. Execute any flow in the system by knowing its flow ID 2. Access potentially sensitive data processed by victim's flows 3. Consume victim's resources Fixes Fixed in PR #12832 (fix(security): close IDOR in get_flow_by_id_or_endpoint_name), merged 2026-04-22, released in Langflow 1.9.1. The helper normalizes user_id once and enforces ownership on both lookup branches (UUID