# CVE-2026-55235

## Summary

- **CVE ID:** CVE-2026-55235
- **Severity:** MEDIUM
- **CVSS Score:** 5.9 (CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:L)
- **CWE:** CWE-287
- **Published:** Sep 14, 2026
- **Last Modified:** Sep 16, 2026

## Description

langgraph-api implements the LangGraph API for rapid development and testing. Prior to 0.10.0, langgraph-api permits a run or cron to specify a relative webhook target that is delivered through an in-process loopback transport, and the authentication middleware treats that transport as internal without applying the authentication context used for external requests. In deployments that rely on per-user authorization to separate threads and runs, an authenticated user can direct a webhook to the server's own thread and run routes, allowing creation of a run on or modification of another user's thread and limited incorporation of the targeted thread's metadata into the created run record. The affected path requires webhook targets and per-user authorization boundaries; deployments that deliberately re-enable loopback delivery should restrict it to controlled same-process routes because those webhooks remain unauthenticated. This issue is fixed in version 0.10.0.

## Affected Products

- langchain-ai — langgraph-api (< 0.10.0)

## References

- [CNA](https://github.com/langchain-ai/helm/security/advisories/GHSA-2c9q-c2q9-qgqv)
- [CNA](https://github.com/langchain-ai/docs/blob/7b70fbacab21f84d9c6f9848f86cdeb471adbb50/src/langsmith/agent-server-changelog.mdx)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.23%
- **EPSS Percentile:** 14.5

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-18._