Summary

The LangGraph Python SDK v3 streaming client interpolates caller-supplied threadid and assistantid 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 gettree and fetchstate implementations build request paths from raw identifiers rather than passing each identifier through the SDK's existing quotepathparam 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"]["threadid"] 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 threadid or assistantid. 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 threadid, the attacker can also control the query string, for example by targeting /store/items?namespace=...&key=...; assistantid 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 langgraph-sdk to version 0.4.6 or later. The fix encodes assistantid in gettree and threadid in fetchstate with quotepathparam in both synchronous and asynchronous stream modules.

If you use RemoteGraph, also upgrade langgraph to version 1.2.14 or later, which requires langgraph-sdk>=0.4.6.

Impact What kind of vulnerability is it? Who is impacted? langgraph-sdk incorrectly applies the actions= argument on resource-scoped authorization decorators, including @auth.on.threads, @auth.on.assistants, and @auth.on.crons.

In affected versions, a decorator such as:

python @auth.on.threads(actions=["create"]) async def allowthreadcreate(ctx, value): return None intended to register a handler for selected actions instead registers that handler for every action on the resource. Because the resource-wide handler is selected before broader fallback handlers, authorization checks implemented in those fallback handlers may not run.

An authenticated user may therefore be able to perform actions the application intended to deny, such as reading, updating, or deleting another user's resource. Exploitability and impact depend on the affected handler's behavior: deployments remain protected if that handler independently enforces the necessary action, ownership, or permission checks for every request it receives.

Only Python deployments using actions= on the affected resource-scoped decorators are affected.

Patches

0.4.4

Workarounds

No.

References

N/A