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.
History

Wed, 06 May 2026 17:30:00 +0000

Type Values Removed Values Added
CPEs cpe:2.3:a:n8n:n8n:*:*:*:*:enterprise:node.js:*:*
cpe:2.3:a:n8n:n8n:2.18.0:*:*:*:enterprise:node.js:*:*
Metrics cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'}


Tue, 05 May 2026 22:00:00 +0000

Type Values Removed Values Added
First Time appeared N8n
N8n n8n
Vendors & Products N8n
N8n n8n

Mon, 04 May 2026 20:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Mon, 04 May 2026 19:00:00 +0000

Type Values Removed Values Added
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.
Title n8n: Unauthenticated Denial of Service via MCP Client Registration
Weaknesses CWE-770
References
Metrics cvssV4_0

{'score': 8.7, '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'}


cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published: 2026-05-04T18:38:51.626Z

Updated: 2026-05-04T19:59:24.621Z

Reserved: 2026-04-25T05:37:12.117Z

Link: CVE-2026-42236

cve-icon Vulnrichment

Updated: 2026-05-04T19:59:13.387Z

cve-icon NVD

Status : Analyzed

Published: 2026-05-04T19:16:06.337

Modified: 2026-05-06T17:16:02.340

Link: CVE-2026-42236

cve-icon Redhat

No data.