LangGraph: Unencoded identifiers in LangGraph SDK v3 streaming can redirect authenticated GET requests

Summary

The LangGraph Python SDK v3 streaming client interpolates caller-supplied thread_id and assistant_id values into request paths without encoding them at four synchronous and asynchronous call sites. Relative path segments can therefore redirect an authenticated GET request to another path on the same configured server.

Details

The affected get_tree and _fetch_state implementations build request paths from raw identifiers rather than passing each identifier through the SDK's existing _quote_path_param helper. HTTP path normalization can collapse values containing relative segments before dispatch while retaining the client's authentication headers.

langgraph-sdk versions 0.4.0 through 0.4.5 are affected. The v3 stream module is not present in the 0.3.x release line.

RemoteGraph v3 streaming in langgraph 1.2.3 and later is also affected when used with a vulnerable langgraph-sdk version. It passes config["configurable"]["thread_id"] into threads.stream(...), and its dependency range permits affected SDK versions.

Impact

An application is affected only if it passes attacker-controlled text as a streaming thread_id or assistant_id. In that configuration, an attacker may select another readable path on the configured server and cause the SDK to return that response to the application. Through thread_id, the attacker can also control the query string, for example by targeting /store/items?namespace=...&key=...; assistant_id controls only the path. The affected requests are GET operations, so this issue does not provide a write primitive.

The LangGraph Platform is not exposed to this issue.

Remediation

Upgrade to version 0.4.6 or later. The fix encodes in and in with in both synchronous and asynchronous stream modules.