How severe is CVE-2026-42236?

No CVSS score has been assigned to CVE-2026-42236 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-42236?

CVE-2026-42236 affects the following packages: n8n (npm), n8n (npm), n8n (npm). Ecosystems affected: npm.

How do I fix CVE-2026-42236?

Update n8n to 1.123.32 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-42236 is resolved across your whole dependency graph.

How do I detect CVE-2026-42236 in my npm dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for n8n, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-42236 if there is no patch (or I can't update yet)?

Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Is CVE-2026-42236 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-42236 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-42236?

CVE-2026-42236 has an EPSS (Exploit Prediction Scoring System) score of 0.5%, placing it in the 42th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-42236?

CVE-2026-42236 is classified as CWE-770 (CWE-770). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-42236 published, and has it been updated?

CVE-2026-42236 was published on May 4, 2026 and was last updated on October 28, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

📦 npm

Not in CISA KEV

CVE-2026-42236 — n8n

CVE-2026-42236 is a CWE-770 vulnerability in n8n. A fix is available for n8n — see the affected versions and patch details below.

n8n: Unauthenticated Denial of Service via MCP Client Registration

Also known asGHSA-49m9-pgww-9vq6

Published

May 4, 2026

Updated

Oct 28, 2026

Affected

3 pkgs

Patched

3 / 3

Exploits

None indexed

Exploitation data as of Nov 4, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-42236.

EPSS Exploitation Probability

via FIRST.org ↗

0.5%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs42th percentile — riskier than 42% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

Real-World Exposure

3 pkgs affected

How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.

36other npm packages depend on this — each one inherits the vulnerability until it's patched upstream

n8nnpm

123Kdownloads / week

Description

Impact

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.

Patches

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.

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.

Affected Packages

3 total 3 fixed

Ecosystem	Package	Vulnerable range	Fix
📦npm	`n8n`	all versions	1.123.32`npm install n8n@1.123.32`
📦npm	`n8n`	≥ 2.18.0&&< 2.18.1	2.18.1`npm install n8n@2.18.1`
📦npm	`n8n`	≥ 2.0.0&&< 2.17.4	2.17.4`npm install n8n@2.17.4`

Affected Products

1 product · 3 configurations

Application

n8nn8n

≥ 2.17.0 && ≤ 2.17.4

1 version

2.18.0

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for n8n, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update n8n to 1.123.32 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-42236 is resolved across your whole dependency graph.
Workarounds
Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Frequently Asked Questions

## Impact 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

O3 Security · Impact-Aware SCA

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CVE-2026-42236 — n8n

Exploitation Status

No confirmed exploitation observed yet

EPSS Exploitation Probability

Real-World Exposure

Description

Impact

Patches

Workarounds

Affected Packages

Affected Products

Detection & mitigation playbook

Detect

Fix

Workarounds

Frequently Asked Questions

Is CVE-2026-42236 in your dependencies?