CVE-2026-126386

n8n’s MCP authorization flow could redirect visitors to an untrusted site

n8n · MCP OAuth client registration

First documented disclosure · Review checkpoint

Summary

The registration flow accepted a redirect destination before completing the instance’s checks. A trusted n8n URL could direct the visitor to a phishing site.

Severity and exploitation evidence

Medium · 5.1/10 · CVSS 4.0. Severity source.

Exploitation not established: The reviewed advisory does not report malicious exploitation.

Exploitation evidence source

Technical severity is not a measure of observed attacks or of risk to your deployment. Attempts, demonstrations, and successful compromise retain the qualifications in the source.

How the weakness works

The registration flow accepted a redirect destination before completing the instance’s checks.

Conditions required

An attacker could reach the default public registration flow and a visitor followed the resulting authorization link.

Potential impact

A trusted n8n URL could direct the visitor to a phishing site.

Affected versions and configurations

1.x before 1.123.89, 2.x before 2.45.5, 2.46.0, and 3.0.0.

Fix and mitigation status

1.123.89, 2.45.5, 2.46.1 or 3.0.1 on the respective release lines.

Practical next steps

Install the corrected release for your branch or restrict public access to the MCP OAuth endpoints.

Operating lesson

Validate redirect destinations before directing the browser to them.

Evidence and limits

The CVE record was published on 2026-11-13.

Sources