CVE-2026-55235Network attack vectorHinoki check available

Cross-user thread modification via unauthenticated loopback webhooks

Published Sep 14, 2026 · Updated Sep 14, 2026

Authentication bypass in LangChain LangGraph API before 0.10.0 allows remote authenticated users to modify another user's thread via webhooks. Relative webhook targets enter the server through an in-process loopback transport that authentication middleware treats as internal, omitting the external request's authentication context. Exposure requires webhook-enabled runs or crons and per-user authorization boundaries; exploitation can create runs, change thread state, and copy limited metadata across users.

CVSS severity5.9
Medium
EPSS probability0.23%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkAvailable
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Authentication bypass in LangChain LangGraph API before 0.10.0 allows remote authenticated users to modify another user's thread via webhooks. Relative webhook targets enter the server through an in-process loopback transport that authentication middleware treats as internal, omitting the external request's authentication context. Exposure requires webhook-enabled runs or crons and per-user authorization boundaries; exploitation can create runs, change thread state, and copy limited metadata across users.

The record

CVE
CVE-2026-55235
Published
Sep 14, 2026
Updated
Sep 14, 2026
Vendor
LangChain
Product
LangGraph API
Classifications
T1190
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Sep 14, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 14, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 0.10.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

LangChain · LangGraph APIversion=< 0.10.0

Published CVSS scores

5.9GitHubCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:L

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1190Exploit Public-Facing Application

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo