CVE-2026-42236: CWE-770: Allocation of Resources Without Limits or Throttling in n8n-io n8n
n8n versions prior to 1. 123. 32, 2. 17. 4, and 2. 18. 1 contain a vulnerability in the MCP OAuth client registration endpoint that allows unauthenticated attackers to send large payloads without resource limits. This can exhaust server memory and cause denial of service. The issue exists because the endpoint accepts unauthenticated requests and does not restrict client registrations even if MCP access is disabled. The vulnerability has been addressed in the specified patched versions.
AI Analysis
Technical Summary
The vulnerability in n8n (CVE-2026-42236) involves the MCP OAuth client registration endpoint accepting unauthenticated requests and storing client data without applying resource usage limits or throttling. This allows a remote unauthenticated attacker to send large registration payloads that can exhaust server memory resources, leading to denial of service. The MCP enable/disable toggle does not restrict access to this endpoint, making it reachable regardless of MCP status. The issue affects versions prior to 1.123.32, 2.17.4, and 2.18.1 and has been fixed in these versions.
Potential Impact
An unauthenticated remote attacker can cause a denial of service by exhausting server memory resources through large payload submissions to the client registration endpoint. This can render the affected n8n instance unavailable until resources are restored or the service is restarted.
Mitigation Recommendations
This vulnerability has been patched in n8n versions 1.123.32, 2.17.4, and 2.18.1. Users should upgrade to these or later versions to remediate the issue. No other mitigation or temporary workaround is indicated in the available data.
CVE-2026-42236: CWE-770: Allocation of Resources Without Limits or Throttling in n8n-io n8n
Description
n8n versions prior to 1. 123. 32, 2. 17. 4, and 2. 18. 1 contain a vulnerability in the MCP OAuth client registration endpoint that allows unauthenticated attackers to send large payloads without resource limits. This can exhaust server memory and cause denial of service. The issue exists because the endpoint accepts unauthenticated requests and does not restrict client registrations even if MCP access is disabled. The vulnerability has been addressed in the specified patched versions.
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The vulnerability in n8n (CVE-2026-42236) involves the MCP OAuth client registration endpoint accepting unauthenticated requests and storing client data without applying resource usage limits or throttling. This allows a remote unauthenticated attacker to send large registration payloads that can exhaust server memory resources, leading to denial of service. The MCP enable/disable toggle does not restrict access to this endpoint, making it reachable regardless of MCP status. The issue affects versions prior to 1.123.32, 2.17.4, and 2.18.1 and has been fixed in these versions.
Potential Impact
An unauthenticated remote attacker can cause a denial of service by exhausting server memory resources through large payload submissions to the client registration endpoint. This can render the affected n8n instance unavailable until resources are restored or the service is restarted.
Mitigation Recommendations
This vulnerability has been patched in n8n versions 1.123.32, 2.17.4, and 2.18.1. Users should upgrade to these or later versions to remediate the issue. No other mitigation or temporary workaround is indicated in the available data.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitHub_M
- Date Reserved
- 2026-04-25T05:37:12.117Z
- Cvss Version
- 4.0
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 69f8eab1cbff5d8610415b93
Added to database: 5/4/2026, 6:51:29 PM
Last enriched: 5/4/2026, 7:06:19 PM
Last updated: 5/4/2026, 7:52:36 PM
Views: 6
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