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CVE-2026-42236

n8n: Unauthenticated Denial of Service via MCP Client Registration

Published: May 4, 2026Updated: May 6, 2026 Sources: CVE List NVD BDUCWE-770
NVD MITRE
7.5CVSSHIGH
EPSS Score
0.5%
Top 63.1%
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
Patch Available

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.

CVSS Vector Breakdown

AV:NAC:LPR:NUI:NS:UC:NI:NA:H
Exploitability
AV:NAttack Vector
Network
AC:LAttack Complexity
Low
PR:NPrivileges Required
None
UI:NUser Interaction
None
Scope
S:UScope
Unchanged
Impact
C:NConfidentiality
None
I:NIntegrity
None
A:HAvailability
High
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Weaknesses

CWE-770

Affected Products

N8nСообщество свободного программного обеспечения
On-premLibrary
OSS Libraries / generic-library
n8nn8n-io
Mixed
Cloud & SaaS / saas-application
n8nn8n
Mixed
Cloud & SaaS / saas-application
сообщество свободного программного обеспеченияoss-projectOperating Systemsaka сообщество свободного программного обеспечения, fsf
n8n-iocommercialDECloud & SaaSaka n8n
n8noss-projectCloud & SaaS

Attack Graph

Products CVE Techniques Tactics

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Exploitability

Official Patch Available

MITRE ATT&CK

1 technique
Impact
View detailed technique mapping

References

https://github.com/n8n-io/n8n/security/advisories/GHSA-49m9-pgww-9vq6
github.com

Timeline

Published
May 4, 2026
Last Updated
May 6, 2026

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