CVE-2026-42236CWE-770

n8n: Unauthenticated Denial of Service via MCP Client Registration

High · published May 4, 2026

CVSS v4.0
8.7
EPSS
1%
Percentile
50.6
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v4.0
8.7 · HIGH
Vector
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
EPSS
0.00651 · 50.6th percentile
Weakness
CWE-770 · Allocation of Resources Without Limits or Throttling
Published
2026-05-04T18:38Z
EPSS history
Timeline
  • 04 MAY 18:38Z
    n8n: Unauthenticated Denial of Service via MCP Client Registration
    cvelistv5