AI agent vulnerability · n8n

CVE-2026-42235: n8n Vulnerable to XSS via MCP OAuth client

highCVSS 4.0 8.8 · 3.1 8.2GHSA-537j-gqpc-p7fq

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.

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: >= 2.17.0, < 2.17.4
Fixed in: 2.17.4
Check: npm ls n8n

Advisory details

From the GitHub Advisory Database (CC BY 4.0).

Impact

An unauthenticated attacker could register a malicious MCP OAuth client with a crafted client_name. 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.

Credited to OscarBataille.

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

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