langgraph-api: Incomplete assistant authorization in LangGraph Server run creation

Story map

Why it is Yellow

• CVSS 5.9 medium
• On your watchlist: PyPI

Affected packages

References

• https://github.com/advisories/GHSA-jfj5-wrj9-63x4
• https://github.com/langchain-ai/helm/security/advisories/GHSA-jfj5-wrj9-63x4
• https://nvd.nist.gov/vuln/detail/CVE-2026-55236
• https://github.com/langchain-ai/docs/blob/7b70fbacab21f84d9c6f9848f86cdeb471adbb50/src/langsmith/agent-server-changelog.mdx
• https://github.com/pypa/advisory-database/tree/main/vulns/langgraph-api/PYSEC-2026-3858.yaml
• https://github.com/advisories/GHSA-jfj5-wrj9-63x4

Original description

## Summary In affected versions of `langgraph-api` (the LangGraph Server runtime), the run-creation path authorized the assistant attached to a run using a different authorization event than the rest of the assistant-handling code paths. Direct assistant reads and cron creation dispatch the `assistants.read` authorization event; run creation dispatched `assistants.search` with an incomplete value. In deployments whose custom authorization handlers register only an `assistants.read` handler (without an `assistants.search` handler and without a global fallback handler), no handler was consulted on the run-creation path, the returned filter set was empty, and the owner constraint was omitted from the resulting query. As a result, in those deployments a request to create a run could reference a private assistant owned by another user, even where direct assistant reads, assistant search, and cron creation against that assistant were correctly denied. The run-creation response merged the referenced assistant's `metadata`, `config`, and `context` into fields returned to the requesting user. These fields can carry sensitive configuration; the runtime encrypts them at rest for that reason. 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), and - use custom authorization handlers that gate assistant access through an `assistants.read` or `assistants.search` handler rather than a global handler covering all assistant events. Deployments without custom authorization handlers, or whose handlers apply an equivalent owner filter across all assistant events (for example through a global handler), are not affected. ## Impact - Confidentiality: exposure of another user's private assistant `metadata`, `config`, and `context` through the run-creation response. These fields can contain sensitive configuration. - Integrity: creation of a run associated with another user's private assistant, beyond the requesting user's authorization scope; the run is then carried out using that assistant's configuration. ## Patches / mitigation Run creation, and the parallel cron-creation path, now dispatch the `assistants.read` authorization event in both the in-memory and gRPC/Postgres runtimes, matching direct assistant reads. Client-supplied run and cron metadata is no longer forwarded into that authorization event, so handlers receive a consistent value shape and determine access by returning an owner filter that is applied server-side. Fixed in `langgraph-api` 0.10.0. This is a behavioral change for deployments with custom authorization handlers: - Handlers that gated assistant access only through `assistants.search` during run creation are no longer consulted on that path; provide an equivalent `assistants.read` handler that returns the same owner filter. - The metadata field on the `assistants.read` event during run and cron creation is no longer populated; handlers that read or stamped it should move that logic into the run/cron create handlers. ## Operational guidance - Register an `assistants.read` handler (or a global handler covering it) that returns an owner-style filter, and confirm parity across the assistant read, search, and run/cron creation paths. - Upgrade to a release containing this change.