CVE-2026-42230: n8n: Open Redirect in MCP OAuth Consent Flow
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; 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.
Other sources
n8n is an open source workflow automation platform. Prior to versions 1.123.32, 2.17.4, and 2.18.1, 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; if the victim clicks "Deny" on the consent page, they are silently redirected to an external site. This issue has been patched in versions 1.123.32, 2.17.4, and 2.18.1.
— MITRE
Affected Software
Event History
Frequently Asked Questions
What is the severity of CVE-2026-42230?
CVE-2026-42230 is a high severity vulnerability due to unauthorized client registration allowing arbitrary redirect URIs.
How do I fix CVE-2026-42230?
To fix CVE-2026-42230, upgrade n8n to version 2.17.4, 2.18.1, or later if using version 2, or to version 1.123.32 if using version 1.
What are the affected versions for CVE-2026-42230?
CVE-2026-42230 affects n8n versions between 2.0.0 and 2.17.4, and up to version 2.18.0, as well as up to version 1.123.32.
What consequences can arise from CVE-2026-42230?
Exploitation of CVE-2026-42230 can lead to unauthorized redirection of users, potentially resulting in phishing attacks.
How can I verify if my system is vulnerable to CVE-2026-42230?
You can verify if your system is vulnerable to CVE-2026-42230 by checking the installed version of n8n against the affected versions listed for the vulnerability.