n8n-io n8n up to 1.123.31/2.17.3/2.18.0 Registration allocation of resources

Summaryinfo

A vulnerability, which was classified as problematic, has been found in n8n-io n8n up to 1.123.31/2.17.3/2.18.0. Affected is an unknown function of the component Registration Handler. The manipulation leads to allocation of resources. This vulnerability is traded as CVE-2026-42236. It is possible to initiate the attack remotely. There is no exploit available. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability, which was classified as problematic, has been found in n8n-io n8n up to 1.123.31/2.17.3/2.18.0. This issue affects an unknown functionality of the component Registration Handler. The manipulation with an unknown input leads to a allocation of resources vulnerability. Using CWE to declare the problem leads to CWE-770. The product allocates a reusable resource or group of resources on behalf of an actor without imposing any restrictions on the size or number of resources that can be allocated, in violation of the intended security policy for that actor. Impacted is availability. The summary by CVE 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.

It is possible to read the advisory at github.com. The identification of this vulnerability is CVE-2026-42236 since 04/25/2026. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. The technical details are unknown and an exploit is not publicly available. The attack technique deployed by this issue is T1499 according to MITRE ATT&CK.

Upgrading to version 1.123.32, 2.17.4 or 2.18.1 eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-27111). Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Productinfo

Vendor

• n8n-io

Name

• n8n

Version

• 1.123.0
• 1.123.1
• 1.123.2
• 1.123.3
• 1.123.4
• 1.123.5
• 1.123.6
• 1.123.7
• 1.123.8
• 1.123.9
• 1.123.10
• 1.123.11
• 1.123.12
• 1.123.13
• 1.123.14
• 1.123.15
• 1.123.16
• 1.123.17
• 1.123.18
• 1.123.19
• 1.123.20
• 1.123.21
• 1.123.22
• 1.123.23
• 1.123.24
• 1.123.25
• 1.123.26
• 1.123.27
• 1.123.28
• 1.123.29
• 1.123.30
• 1.123.31
• 2.0
• 2.1
• 2.2
• 2.3
• 2.4
• 2.5
• 2.6
• 2.7
• 2.8
• 2.9
• 2.10
• 2.11
• 2.12
• 2.13
• 2.14
• 2.15
• 2.16
• 2.17
• 2.17.0
• 2.17.1
• 2.17.2
• 2.17.3
• 2.18.0

Website

• Product: https://github.com/n8n-io/n8n/

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Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

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