GHSA-2c9q-c2q9-qgqv: Medium severity pip/langgraph-api vulnerability
Summary
In affected versions of langgraph-api (the LangGraph Server runtime), a run or cron could be created with a relative webhook target. When the server later delivers such a webhook, it routes the request back into the same application through an in-process loopback transport that the authentication middleware treats as internal and does not authenticate. As a result, a relative webhook target could reach the server's own routes that operate on threads and runs without the authentication context that applies to ordinary external requests.
In deployments that scope threads and runs by owner, this could allow a request associated with one user to reach routes operating on another user's thread, resulting in creation of a run on (or modification of the state of) a thread owned by another user, even where the corresponding direct external requests were correctly denied. Limited metadata from the targeted thread may be incorporated into the created run record.
We have no evidence of this behavior occurring in the wild.
Affected users / systems
You may be affected if you:
- run langgraph-api (the LangGraph Server / Agent Server runtime, including via the LangGraph Platform Helm chart), - allow runs or crons to specify webhook targets, and - rely on per-user authorization to separate threads and runs between users.
Impact
- Integrity: creation of a run on, or modification of the state of, a thread owned by another user, beyond the requesting user's authorization scope. - Confidentiality: limited exposure of another user's thread metadata, incorporated into the created run record.
Patches / mitigation
The webhook URL policy now denies loopback delivery by default: the webhooks.url.disableloopback policy defaults to enabled. This covers relative webhook targets routed through the in-process transport, as well as localhost-style hostnames, loopback address ranges, and hostnames that resolve into the loopback range. Deployments that legitimately deliver webhooks to a route hosted on the same process can opt back in by setting webhooks.url.disableloopback: false in langgraph.json (or the equivalent LANGGRAPHWEBHOOKS configuration); do so only when you control the routes those webhooks reach, as they are delivered without authentication. Fixed in langgraph-api 0.10.0.
Operational guidance
- Upgrade to a release containing this change and keep loopback webhook delivery disabled unless required. - If loopback delivery is enabled, restrict it to routes you control and apply authorization within those routes.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
pip/langgraph-apito a version that resolves this vulnerability.Fixed in 0.10.0 - Upgrade
Upgrade
langgraph-apito a version that resolves this vulnerability.Fixed in 0.10.0 - Configuration
Set `webhooks.url.disable_loopback` to enabled (default) in `langgraph.json` (or `LANGGRAPH_WEBHOOKS`) to deny loopback webhook delivery. Only opt back in by setting it to `false` if you control all routes reached by those webhooks, since delivery occurs without the usual authentication context.
LangGraph Server / Agent Server (langgraph-api) webhooks.url.disable_loopback = true - Configuration
Ensure runs/threads are scoped by owner and enforce per-user authorization so requests cannot create or modify runs/threads owned by another user beyond the requesting user's authorization scope.
Thread/Run authorization model per-user authorization scope = enforced
Event History
Frequently Asked Questions
What does an attacker need to exploit this issue?
The attacker needs network access and low privileges sufficient to create a run or cron with a relative webhook target. Exploitation also requires the higher-complexity condition of causing the server to later deliver that webhook.
Which deployments face the greatest impact?
Deployments that scope threads and runs by owner are particularly affected. In those environments, a request associated with one user may create a run on, or modify the state of, another user’s thread despite direct external requests being denied.
What can the attacker access or change through the bypass?
The relative webhook can reach internal routes that operate on threads and runs without the authentication context applied to ordinary external requests. This can result in a run being created on another owner’s thread or modification of that thread’s state; limited metadata from the targeted thread may also be incorporated into the created run record.