CVE-2026-42236
Description
n8n is an open source workflow automation platform. Prior to versions 1.123.32, 2.17.4, and 2.18.1, the MCP OAuth client registration endpoint accepted unauthenticated requests and stored client data without adequate resource controls. An unauthenticated remote attacker could exhaust server memory resources by sending large registration payloads, rendering the n8n instance unavailable. The MCP enable/disable toggle gates MCP access but did not restrict client registrations, meaning the endpoint is reachable regardless of whether MCP access is enabled on the instance. This issue has been patched in versions 1.123.32, 2.17.4, and 2.18.1.
How to fix
- n8n n8n1.123.32 or later
- n8n1.123.32, 2.18.1, 2.17.4 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| n8n n8n | v < 1.123.32, 2.17.0 ≤ v ≤ 2.17.4, 2.18.0 | 1.123.32 |
| n8nnpm | v < 1.123.32, 2.18.0 ≤ v < 2.18.1, 2.0.0 ≤ v < 2.17.4 | 1.123.32, 2.18.1, 2.17.4 |
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