Resource exhaustion in N8n

CVE-2026-42236

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.

Published · last modified .

CVSS v3 metric

CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

EPSS exploit prediction

EPSS: 0.007 (49.2th percentile), scored .

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 49th percentile — 49.2% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS trend (30 days)EPSS over the last 30 days for CVE-2026-42236: held from 0.005 to 0.007.

EPSS over last 30 days · oldest: 0.005 · newest: 0.007 · change: +0.002

Affected products

  • N8n — versions 2.18.0
  • N8n-Io N8n — versions < 1.123.32, >= 2.17.0, < 2.17.4, >= 2.18.0, < 2.18.1

Weakness classification (CWE)

References

Frequently asked questions

What is CVE-2026-42236?
CVE-2026-42236 is a high-severity vulnerability in N8n, classified under Allocation of Resources Without Limits or Throttling. CVSS score: 7.5/10. Published 2026-05-04.
How severe is CVE-2026-42236?
High severity. CVSS v3 base score is 7.5 out of 10.