What’s Vulnerable › Vulnerabilities
CVE-2026-42235: n8n: XSS via MCP OAuth client
- Severity: critical (CVSS 9.6 v3.1)
- Exploited in the wild: not listed in CISA KEV
- EPSS: 0.3% probability of exploitation in the next 30 days
- Public exploit or detection template: none known
- Published: 2026-05-04 · updated 2026-06-17
- Weakness: CWE-79
Description
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 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. This issue has been patched in versions 1.123.32, 2.17.4, and 2.18.1.
Affected products
- n8n-io n8n: before 1.123.32; from 2.17.0 before 2.17.4; 2.18.0 — fixed in 1.123.32, 2.17.4
How to fix
Upgrade to a fixed version: n8n-io n8n 1.123.32, 2.17.4. Check the vendor advisory for mitigations.
References
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