CVE-2026-126386: n8n before 1.123.89 Open Redirect via MCP OAuth Dynamic Client Registration
n8n before 1.123.89, 2.x before 2.45.5, 2.46.x before 2.46.1, and 3.x before 3.0.1 contains an open redirect vulnerability in the unauthenticated MCP OAuth dynamic client registration flow, which accepts arbitrary redirecturi values via the /mcp-oauth/register endpoint. Attackers can send victims crafted /mcp-oauth/authorize URLs that redirect them to attacker-controlled sites before instance checks run, enabling phishing.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Fixed in 1.123.89 - Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Fixed in 2.45.5 - Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Fixed in 2.46.1 - Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Fixed in 3.0.1
Event History
Frequently Asked Questions
Which deployments are affected?
Affected versions are n8n before 1.123.89, 2.x before 2.45.5, 2.46.x before 2.46.1, and 3.x before 3.0.1. The issue is in the unauthenticated MCP OAuth dynamic client registration flow exposed through the /mcp-oauth/register endpoint.
What does an attacker need to exploit this issue?
An attacker does not need authentication or prior privileges. They need to craft an /mcp-oauth/authorize URL and persuade a victim to visit it; the redirect can then send the victim to an attacker-controlled site.
What is the practical impact?
The primary impact described is phishing. The redirect occurs before instance checks run, which can make attacker-controlled destinations appear to be reached through a legitimate n8n OAuth flow.