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N8nApplication

CVE-2026-42236

HIGH · 7.5 CVSS v3.1 Published 2026-05-04
Fix available
A fix is available. Upgrade to 1.123.32 or later.
See remediation →
84/100
Remediation priority · High
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

The MCP OAuth client registration endpoint in n8n accepts unauthenticated requests and stores client data without adequate resource controls, allowing an unauthenticated remote attacker to exhaust server memory by sending large registration payloads, rendering the n8n instance unavailable.

MitigationUpgrade to n8n versions 1.123.32, 2.17.4, or 2.18.1 which contain the patch. As a workaround, implement network-level access controls to limit exposure to the MCP client registration endpoint until the upgrade can be performed.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
N8nApplication
Affected:< 1.123.32>= 2.17.0, <= 2.17.4= 2.18.0

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify installed n8n version
    Check the version displayed in the n8n UI footer or query the API endpoint /healthz. In self-hosted deployments, inspect the package.json file or the Docker image tag.
    Affected if The installed version is less than 1.123.32, or falls between 2.17.0 and 2.17.4 inclusive, or equals 2.18.0.
  2. Confirm MCP OAuth feature is enabled
    Verify that the MCP OAuth client registration endpoint is available on the instance. This endpoint is typically accessible at the /api/mcp/oauth/ routes. Attempt a request to the client registration endpoint or check server logs for MCP-related route registration.
    Affected if The MCP OAuth endpoint responds to requests, indicating the vulnerable feature is active.
  3. Assess network exposure of the registration endpoint
    Review firewall rules, reverse proxy configuration, or cloud security group settings to determine whether the MCP OAuth client registration endpoint is accessible from untrusted networks or the public internet.
    Affected if The endpoint is reachable without authentication from external networks without any access restrictions.

A user is affected if their n8n instance runs a version in the affected ranges, has the MCP OAuth feature enabled, and the endpoint is exposed to unauthenticated network access.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 1.123.32 or later
Fixed in 1.123.32
Interim mitigation

Upgrade to n8n versions 1.123.32, 2.17.4, or 2.18.1 which contain the patch. As a workaround, implement network-level access controls to limit exposure to the MCP client registration endpoint until the upgrade can be performed.

Recommended fix High confidence

1.123.32 (for 1.x users) OR 2.17.4 (for 2.17.x users) OR 2.18.1 (for 2.18.0 users)

  1. 1. Identify your current n8n version by checking the instance or running `n8n --version`
  2. 2. If running on version 1.x (below 1.123.32), plan upgrade to version 1.123.32
  3. 3. If running on version 2.17.0-2.17.4, plan upgrade to version 2.17.4
  4. 4. If running on version 2.18.0, plan upgrade to version 2.18.1
  5. 5. Take a backup of the n8n database and configuration files before upgrading
  6. 6. Stop the n8n service
  7. 7. Upgrade n8n using your deployment method (Docker, npm, or binary)
  8. 8. Verify the new version is running: `n8n --version`
Caveat n8n upgrades are generally backward compatible but test in a staging environment before production deployment; review n8n release notes for any changes relevant to your workflows

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in N8n Scoped from the published advisory
  • Consultation2.0 h
  • Implementation2.0 h
  • Testing2.0 h
  • Review / QA1.0 h
7.0 hours of engineering $1,240
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-42236 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data