CVE-2026-118668: Authorization Bypass in LangGraph Handlers

CVE-2026-118668 affects langgraph-api versions 0.1.2 through versions prior to 0.15.0. JavaScript and TypeScript custom authentication handlers fail to carry the rewritten namespace across the runtime boundary, preventing its application before Store operations. Authenticated users can therefore access other users' namespaces when deployments rely on namespace rewriting for isolation, compromising data confidentiality and integrity.

The vulnerability carries a CVSS score of 8.6 with declared severity high, indicating significant impact. The defect permits unauthorized reads, overwrites, searches, and deletions of other users' data. Importantly, Python custom authentication handlers and those that reject unauthorized namespaces instead of rewriting them are not affected. The status is resolved: version 0.15.0 implements the fix. The vulnerability was discovered by Coinspect researchers with coherent social media signals beginning today, October 29, 2026.

Administrators and security teams must urgently verify whether their LangGraph deployments use custom authentication handlers written in JavaScript or TypeScript that implement namespace rewriting. If present, upgrade immediately to version 0.15.0 or later. For deployments still on earlier versions, implement additional isolation controls at the application level until upgrade completion. Review access logs to Store operations for anomalous access patterns to namespaces other than those assigned to the user.

This vulnerability highlights a critical aspect of multi-tenant systems that rely on dynamic rewriting of security parameters—in this case, namespace for isolation. The assumption that a rewritten value remains consistent across a runtime boundary is a recurring error pattern. Administrators should review similar architectural patterns in their deployments to identify potential related weaknesses.