AI agent vulnerability · n8n

CVE-2026-42230: n8n has Open Redirect in MCP OAuth Consent Flow

mediumCVSS 4.0 5.1 · 3.1 4.7GHSA-f6x8-65q6-j9m9

Impact The /mcp-oauth/register endpoint accepted OAuth client registrations without authentication, allowing arbitrary redirecturi values to be registered. When a user denies the MCP OAuth consent dialog, the handleDeny handler redirects the user to the registered redirecturi without validation, enabling an open redirect to an attacker-controlled URL. An attacker can craft a phishing link and send it to a victim;

Published Apr 29, 2026 · Updated May 8, 2026

Affected packages

n8n

Ecosystem: npm
Affected: < 1.123.32
Fixed in: 1.123.32
Check: npm ls n8n

n8n

Ecosystem: npm
Affected: >= 2.18.0, < 2.18.1
Fixed in: 2.18.1
Check: npm ls n8n

n8n

Ecosystem: npm
Affected: >= 2.0.0, < 2.17.4
Fixed in: 2.17.4
Check: npm ls n8n

Advisory details

From the GitHub Advisory Database (CC BY 4.0).

Impact

The /mcp-oauth/register endpoint accepted OAuth client registrations without authentication, allowing arbitrary redirect_uri values to be registered. When a user denies the MCP OAuth consent dialog, the handleDeny handler redirects the user to the registered redirect_uri without validation, enabling an open redirect to an attacker-controlled URL. An attacker can craft a phishing link and send it to a victim; if the victim clicks "Deny" on the consent page, they are silently redirected to an external site.

Patches

The issue has been fixed in n8n versions 1.123.32, 2.17.4, and 2.18.1. Users should upgrade to one of these versions or later to remediate the vulnerability.

Workarounds

If upgrading is not immediately possible, administrators should consider the following temporary mitigations:

Restrict network access to the n8n instance to prevent untrusted users from reaching the MCP OAuth endpoints.
Limit access to the n8n instance to fully trusted users only.

These workarounds do not fully remediate the risk and should only be used as short-term mitigation measures.

Credited to ori-ron.

References

How this page is made: the data panel comes from the GitHub Advisory Database, CISA’s KEV catalog, the NVD and FIRST EPSS, and updates twice a day. No analysis has been written for this entry yet. Methodology

More n8n vulnerabilities

All n8n entries