CVE-2026-55235
Received Received - Intake

Authentication Bypass in LangGraph API via Loopback Webhook

Publication date: 2026-09-14

Last updated on: 2026-09-14

Assigner: GitHub, Inc.

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.

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Meta Information

Published
2026-09-14
Last Modified
2026-09-14
Generated
2026-09-15
AI Q&A
2026-09-14
EPSS Evaluated
N/A
NVD
CVE-2026-55235
EUVD
EUVD-2026-77585

Affected Vendors & Products

Showing 2 associated CPEs
Vendor Product Version / Range
langgraph langgraph-api to 0.10.0 (exc)
langgraph-ai langgraph-api to 0.10.0 (exc)

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-287 When an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct.

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Executive Summary

This vulnerability affects langgraph-api versions before 0.10.0. It allows authenticated users to create webhook targets that deliver requests to internal server routes without proper authentication. This bypasses authorization checks, enabling users to create or modify runs and threads belonging to other users, potentially exposing limited metadata.

Detection Guidance

Check the version of langgraph-api running on your system. If it is below 0.10.0, the system is vulnerable. Use commands like 'pip show langgraph-api' or inspect your deployment logs for version information.

Impact Analysis

If you use langgraph-api prior to 0.10.0 with per-user authorization, an attacker could manipulate your threads or runs by exploiting unauthenticated loopback webhooks. This could lead to unauthorized data access or modifications across user boundaries, though exploitation requires specific conditions like webhook targets and per-user authorization.

Compliance Impact

This vulnerability could violate compliance by allowing unauthorized access or modification of user data across authorization boundaries. It risks breaching confidentiality and integrity requirements in GDPR and HIPAA, especially in multi-user deployments where per-user authorization is critical.

Mitigation Strategies

Upgrade langgraph-api to version 0.10.0 or later immediately. If you must use an older version, disable loopback delivery for webhooks and restrict webhook targets to controlled same-process routes.

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