43/100 CVSS 7.5 🔴 CVE ANALYSISPublished: April 29, 2026

n8n Vulnerable to Unauthenticated Denial of Service via MCP Client Registration

## 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 ...

7.5

CVSS Score

LOW

Threat Level

Priority /100

TBD

Exploited ITW

Monitor

CISA Status

Sources

🔵

HIGH-PRIORITY SECURITY ADVISORY — Priority Score: 43/100

CVSS 7.5 LOW. SENTINEL APEX recommends immediate patch evaluation. Intelligence from 1 confirmed source(s).

📋 Executive Summary

⚡ Analyst Assessment — SENTINEL APEX v4.0

CYBERDUDEBIVASH SENTINEL APEX has confirmed a LOW-tier threat intelligence signal for CVE-2026-42236 affecting npm n8n. Composite threat score: 43/100. Intelligence corroborated across 1 source(s): github_advisories. CVSS base score: 7.5. Exploitation probability assessed as HIGH based on vulnerability characteristics.

Intelligence sources: github_advisories

⚠️ Business Impact Analysis

⚠️ Remote code execution — full server takeover without authentication possible
⚠️ Authentication bypass — all access controls circumvented

🔗 Attack Chain Analysis

Step-by-step attack chain based on observed TTPs and vulnerability characteristics:

#	Phase	Attacker Action	MITRE
1	Reconnaissance	Attacker identifies exposed n8n instances via Shodan, Censys, or targeted scanning	`TA0043`
2	Initial Access	Unauthenticated exploitation — no credentials required. Single HTTP request sufficient	`T1190`
3	Execution	Remote code execution achieved — attacker runs arbitrary commands on target system	`T1203`
4	Persistence	Backdoor, scheduled task, or new admin account created for persistent access	`T1053`
5	Command & Control	Attacker establishes persistent C2 channel using HTTPS or DNS tunneling	`T1071`
6	Impact / Objectives	Intellectual property theft, espionage, cryptomining, or preparation for future attack stage	`T1657`

⚠ Deep Dive Analysis

This high-severity vulnerability in npm n8n (CVSS 7.5) represents a significant attack surface. SENTINEL APEX assesses exploitation to be technically feasible with moderate effort. Organizations running n8n in internet-facing or privileged positions face immediate risk.

SENTINEL APEX URGENCY: ELEVATED. Score: 43/100 LOW. Patch before exploitation activity begins.

🎯 MITRE ATT&CK Mapping

Category	Mapping
Primary Tactic	Execution
Primary Technique	T1203 — Exploitation for Client Execution
Sub-Technique	T1059 — Command & Scripting Interpreter
Weakness (CWE)	CWE-770
Intel Type	🔴 CVE ANALYSIS
Source(s)	github_advisories

🔴 CVE Reference

CVE ID	Reference	Score
CVE-2026-42236	NVD →	7.5
CVE-2026-42236	NVD →	7.5

🔍 Detection Rules — Sigma (SIEM)

Deploy to Splunk, Elastic, Microsoft Sentinel, or QRadar. SOC Pro subscribers receive pre-compiled SIEM-native query packs updated with each pipeline run.

Sigma YAMLtitle: CVE-2026-42236 Exploitation Attempt — npm n8n
id: 90dcf2ba18de21be-298e
status: experimental
description: Detects exploitation of CVE-2026-42236 in npm n8n. Priority: LOW. Score: 43/100
author: CYBERDUDEBIVASH SENTINEL APEX v4.0 (bivash@cyberdudebivash.com)
date: 2026-04-29
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2026-42236
    - https://blog.cyberdudebivash.in/
tags:
    - attack.initial_access
    - attack.t1190
    - cve-2026-42236
    - cve-2026-42236
logsource:
    category: webserver
detection:
    keywords:
        - 'CVE-2026-42236'
        - 'CVE-2026-42236'
        - 'cve-2026-42236'
    condition: keywords
falsepositives:
    - Security scanners
level: medium

📡 Detection Rules — YARA (Endpoint)

Deploy to endpoint detection platforms. Enterprise subscribers receive tuned, FP-validated YARA rule packs.

YARArule CVE_2026_42236_Exploitation {
    meta:
        description = "Detects artifacts related to CVE-2026-42236 exploitation in npm n8n"
        author      = "CYBERDUDEBIVASH SENTINEL APEX v4.0"
        date        = "2026-04-29"
        severity    = "HIGH"
        cvss        = "7.5"
        priority    = "43/100"
        threat_level = "LOW"
        reference   = "https://nvd.nist.gov/vuln/detail/CVE-2026-42236"
    strings:
        $id_str  = "CVE-2026-42236" ascii nocase
        $product = "n8n" ascii nocase wide
    condition:
        any of them
}

🛡️ SOC Response Playbook

1IMMEDIATE (0-1hr): Identify all instances of n8n in your environment via CMDB/asset inventory
2IMMEDIATE (0-1hr): Apply vendor patch — no maintenance window exception for LOW threats
3IMMEDIATE (1-2hr): If no patch available: implement WAF rules, ACLs, or network-level compensating controls
4SHORT-TERM (2-4hr): Deploy Sigma detection rule to SIEM — validate alert generation in test environment
5SHORT-TERM (4-8hr): Review logs for exploitation indicators (anomalous n8n requests, error spikes)
6SHORT-TERM (8-24hr): Hunt for post-exploitation: new admin accounts, scheduled tasks, lateral movement
7MONITOR: Subscribe to npm security advisories for patch updates
8ONGOING: Track SENTINEL APEX intelligence feed for follow-on campaigns targeting n8n

📎 Intelligence References

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Related Resources — SENTINEL APEX

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⚡ CYBERDUDEBIVASH SENTINEL APEX v4.0

Intelligence report generated by CYBERDUDEBIVASH SENTINEL APEX v4.0
Report ID: SENTINEL-CVE-2026-42236-2026-04-29 | Priority: 43/100 LOW | Sources: 1
© 2026 CYBERDUDEBIVASH PRIVATE LIMITED
Republication requires written attribution to CYBERDUDEBIVASH SENTINEL APEX

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