CVE-2026-42236

Workarounds

If upgrading is not immediately possible, administrators should consider the following temporary mitigations:

• Restrict network access to the n8n instance to prevent requests from untrusted sources.
• Reduce the maximum accepted payload size by lowering the N8N_PAYLOAD_SIZE_MAX environment variable from its default value.

These workarounds do not fully remediate the risk and should only be used as short-term mitigation measures.

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.

The patches address the unbound registration with an upper bound of registered clients and disabling creation when MCP is disabled on the instance. Mean to restrict the payload size of requests already exist and can be used to control additional risks.

The application allocates resources such as memory, threads, or file descriptors based on untrusted input without enforcing a cap. Typical impact: resource exhaustion leading to denial of service.

CVE-2026-42236 has a CVSS score of 7.5 (High). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (1.123.32, 2.18.1, 2.17.4); upgrading removes the vulnerable code path.

Kodem intelligence

The issue has been fixed in n8n versions 1.123.32, 2.17.4, and 2.18.1. Users should upgrade to one of these versions or later to remediate the vulnerability.

1. What is CVE-2026-42236? CVE-2026-42236 is a high-severity allocation of resources without limits or throttling vulnerability in n8n (npm), affecting versions < 1.123.32. It is fixed in 1.123.32, 2.18.1, 2.17.4. The application allocates resources such as memory, threads, or file descriptors based on untrusted input without enforcing a cap.
2. How severe is CVE-2026-42236? CVE-2026-42236 has a CVSS score of 7.5 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of n8n are affected by CVE-2026-42236? n8n (npm) versions < 1.123.32 is affected.
4. Is there a fix for CVE-2026-42236? Yes. CVE-2026-42236 is fixed in 1.123.32, 2.18.1, 2.17.4. Upgrade to this version or later.
5. Is CVE-2026-42236 exploitable, and should I be worried? Whether CVE-2026-42236 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-42236 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-42236?
   • Upgrade n8n to 1.123.32 or later
   • Upgrade n8n to 2.18.1 or later
   • Upgrade n8n to 2.17.4 or later