CVE-2026-42235: n8n: XSS via MCP OAuth client
Impact An unauthenticated attacker could register a malicious MCP OAuth client with a crafted clientname. If a victim user authorized the OAuth consent dialog and a second user subsequently revoked that access, a toast notification would render the injected script. Clicking the link would execute arbitrary JavaScript in the victim's authenticated n8n browser session, enabling credential and session token theft, workflow manipulation, or privilege escalation.
Patches This issue has been fixed in n8n version 2.14.2. Users should upgrade to this version or later to remediate the vulnerability.
Workarounds If upgrading is not immediately possible, administrators should consider the following temporary mitigations: - Restrict access to the n8n instance and the MCP OAuth registration endpoint to trusted users only. - Disable MCP server functionality if it is not actively required.
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, an unauthenticated attacker could register a malicious MCP OAuth client with a crafted clientname. If a victim user authorized the OAuth consent dialog and a second user subsequently revoked that access, a toast notification would render the injected script. Clicking the link would execute arbitrary JavaScript in the victim's authenticated n8n browser session, enabling credential and session token theft, workflow manipulation, or privilege escalation. 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-2026-42235?
The severity of CVE-2026-42235 is considered medium due to the potential for cross-site scripting (XSS) attacks.
How do I fix CVE-2026-42235?
To fix CVE-2026-42235, upgrade to n8n versions 2.17.4, 2.18.1, or 1.123.32 or later.
What kind of attacks does CVE-2026-42235 facilitate?
CVE-2026-42235 facilitates cross-site scripting (XSS) attacks through unauthorized OAuth client registration.
Who is affected by CVE-2026-42235?
Users of n8n versions between 2.17.0 and 2.17.4, 2.18.0 and 2.18.1, and versions prior to 1.123.32 are affected by CVE-2026-42235.
Can CVE-2026-42235 be exploited without authentication?
Yes, CVE-2026-42235 can be exploited by unauthenticated attackers, increasing the risk of user exposure.