AI-written code allowed missing tenant headers to silently fall back to process-level n8n credentials, risking cross-tenant data exposure.

@@ -1,7 +1,14 @@ #!/usr/bin/env node /**- * Fixed HTTP server for n8n-MCP that properly handles StreamableHTTPServerTransport initialization- * This implementation ensures the transport is properly initialized before handling requests+ * @deprecated This fixed HTTP server is deprecated as of v2.31.8.+ * Use SingleSessionHTTPServer from http-server-single-session.ts instead.+ *+ * This implementation does not support SSE streaming required by clients like OpenAI Codex.+ * See: https://github.com/czlonkowski/n8n-mcp/issues/524+ *+ * Original purpose: Fixed HTTP server for n8n-MCP that properly handles+ * StreamableHTTPServerTransport initialization by bypassing it entirely.+ * This implementation ensures the transport is properly initialized before handling requests.  */ import express from 'express';

 import { Server } from '@modelcontextprotocol/sdk/server/index.js';@@ -125,7 +132,18 @@ async function shutdown() {   }

 } +/**+ * @deprecated Use SingleSessionHTTPServer from http-server-single-session.ts instead.+ * This function does not support SSE streaming required by clients like OpenAI Codex.+ */ export async function startFixedHTTPServer() {+  // Log deprecation warning+  logger.warn(+    'DEPRECATION: startFixedHTTPServer() is deprecated as of v2.31.8. ' ++    'Use SingleSessionHTTPServer which supports SSE streaming. ' ++    'See: https://github.com/czlonkowski/n8n-mcp/issues/524'+  );+

   validateEnvironment();      const app = express();

@@ -71,10 +71,12 @@ const testCases: TestCase[] = [     }   },   {

-    name: 'Fixed HTTP implementation',+    // DEPRECATED: This test case tests the deprecated fixed HTTP implementation+    // See: https://github.com/czlonkowski/n8n-mcp/issues/524

+    name: 'Fixed HTTP implementation (DEPRECATED)',     env: {       MCP_MODE: 'http',-      USE_FIXED_HTTP: 'true',+      USE_FIXED_HTTP: 'true',  // DEPRECATED: Will be removed in future version       AUTH_TOKEN: 'test-token-for-testing-only',       PORT: '3005',       BASE_URL: 'https://fixed.example.com'

@@ -124,9 +124,23 @@ Learn more: https://github.com/czlonkowski/n8n-mcp/blob/main/PRIVACY.md     checkpoints.push(STARTUP_CHECKPOINTS.MCP_HANDSHAKE_STARTING);          if (mode === 'http') {-      // Check if we should use the fixed implementation+      // Check if we should use the fixed implementation (DEPRECATED)       if (process.env.USE_FIXED_HTTP === 'true') {-        // Use the fixed HTTP implementation that bypasses StreamableHTTPServerTransport issues+        // DEPRECATION WARNING: Fixed HTTP implementation is deprecated+        // It does not support SSE streaming required by clients like OpenAI Codex+        logger.warn(+          'DEPRECATION WARNING: USE_FIXED_HTTP=true is deprecated as of v2.31.8. ' ++          'The fixed HTTP implementation does not support SSE streaming required by clients like OpenAI Codex. ' ++          'Please unset USE_FIXED_HTTP to use the modern SingleSessionHTTPServer which supports both JSON-RPC and SSE. ' ++          'This option will be removed in a future version. See: https://github.com/czlonkowski/n8n-mcp/issues/524'+        );+        console.warn('\n⚠️  DEPRECATION WARNING ⚠️');+        console.warn('USE_FIXED_HTTP=true is deprecated as of v2.31.8.');+        console.warn('The fixed HTTP implementation does not support SSE streaming.');+        console.warn('Please unset USE_FIXED_HTTP to use SingleSessionHTTPServer.');+        console.warn('See: https://github.com/czlonkowski/n8n-mcp/issues/524\n');++        // Use the deprecated fixed HTTP implementation

         const { startFixedHTTPServer } = await import('../http-server');         await startFixedHTTPServer();       } else {

@@ -78,6 +78,12 @@ export abstract class BaseTriggerHandler<T extends BaseTriggerInput = BaseTrigge     if (this.context?.n8nApiUrl) {       return this.context.n8nApiUrl.replace(/\/api\/v1\/?$/, '');     }+    // SECURITY (GHSA-jxx9-px88-pj69): in multi-tenant mode, refuse to fall+    // back to the operator's env URL. A handler running without a tenant+    // context must not surface the operator's instance URL.+    if (process.env.ENABLE_MULTI_TENANT === 'true') {+      return undefined;+    }     // Fallback to environment config

     const config = getN8nApiConfig();     if (config?.baseUrl) {@@ -94,6 +100,11 @@ export abstract class BaseTriggerHandler<T extends BaseTriggerInput = BaseTrigge     if (this.context?.n8nApiKey) {       return this.context.n8nApiKey;

     }+    // SECURITY (GHSA-jxx9-px88-pj69): in multi-tenant mode, refuse to fall+    // back to the operator's env API key.+    if (process.env.ENABLE_MULTI_TENANT === 'true') {+      return undefined;+    }     // Fallback to environment config

     const config = getN8nApiConfig();     return config?.apiKey;

@@ -332,6 +332,14 @@ export function getN8nApiClient(context?: InstanceContext): N8nApiClient | null     return null;   } +  // SECURITY (GHSA-jxx9-px88-pj69): never fall back to process-level credentials+  // when multi-tenant mode is enabled. A missing or incomplete tenant context+  // must result in no client, not the operator's N8N_API_KEY.+  if (process.env.ENABLE_MULTI_TENANT === 'true') {+    logger.warn('Refusing env-credential fallback in multi-tenant mode');+    return null;+  }

+   // Fall back to default singleton from environment   logger.info('Falling back to environment configuration for n8n API client');   const config = getN8nApiConfig();@@ -372,6 +380,27 @@ function ensureApiConfigured(context?: InstanceContext): N8nApiClient {   return client; } +/**+ * Resolve the n8n API config to surface in a tool response (apiUrl,+ * baseUrl for workflow links, etc.). Prefers the per-request tenant+ * context; falls back to the process-env config only in single-tenant+ * mode.+ *+ * SECURITY (GHSA-jxx9-px88-pj69): in multi-tenant mode this never returns+ * the operator's env config, so handler responses cannot disclose the+ * operator's apiUrl to a tenant whose context was missing or incomplete.+ */+function resolveN8nApiConfigForResponse(context?: InstanceContext) {+  const fromContext = context ? getN8nApiConfigFromContext(context) : null;

+  if (fromContext) {+    return fromContext;+  }+  if (process.env.ENABLE_MULTI_TENANT === 'true') {+    return null;+  }+  return getN8nApiConfig();

+}+ // MCP transports may serialize JSON objects/arrays as strings. // Parse them back, but return the original value on failure so Zod reports a proper type error. export function tryParseJson(val: unknown): unknown {@@ -1719,7 +1748,7 @@ export async function handleHealthCheck(context?: InstanceContext): Promise<McpT       instanceId: health.instanceId,       n8nVersion: health.n8nVersion,       features: health.features,-      apiUrl: getN8nApiConfig()?.baseUrl,+      apiUrl: resolveN8nApiConfigForResponse(context)?.baseUrl,       mcpVersion,       supportedN8nVersion,       versionCheck: {@@ -1779,7 +1808,7 @@ export async function handleHealthCheck(context?: InstanceContext): Promise<McpT         error: getUserFriendlyErrorMessage(error),         code: error.code,         details: {-          apiUrl: getN8nApiConfig()?.baseUrl,+          apiUrl: resolveN8nApiConfigForResponse(context)?.baseUrl,           hint: 'Check if n8n is running and API is enabled',           troubleshooting: [             '1. Verify n8n instance is running',@@ -1983,10 +2012,14 @@ export async function handleDiagnostic(request: any, context?: InstanceContext):   const isDocker = process.env.IS_DOCKER === 'true';   const cloudPlatform = detectCloudPlatform(); -  // Check environment variables+  // Check environment variables. SECURITY (GHSA-jxx9-px88-pj69): in

+  // multi-tenant mode the operator's env credentials are not part of the+  // tenant's view of the system, so we mask them out of the diagnostic+  // payload rather than letting them leak through `environment.*`.+  const isMultiTenant = process.env.ENABLE_MULTI_TENANT === 'true';   const envVars = {-    N8N_API_URL: process.env.N8N_API_URL || null,-    N8N_API_KEY: process.env.N8N_API_KEY ? '***configured***' : null,+    N8N_API_URL: isMultiTenant ? null : (process.env.N8N_API_URL || null),+    N8N_API_KEY: isMultiTenant ? null : (process.env.N8N_API_KEY ? '***configured***' : null),     NODE_ENV: process.env.NODE_ENV || 'production',     MCP_MODE: mcpMode,     isDocker,

@@ -1996,7 +2029,7 @@ export async function handleDiagnostic(request: any, context?: InstanceContext):   };    // Check API configuration-  const apiConfig = getN8nApiConfig();+  const apiConfig = resolveN8nApiConfigForResponse(context);   const apiConfigured = apiConfig !== null;   const apiClient = getN8nApiClient(context); @@ -2567,7 +2600,7 @@ export async function handleDeployTemplate(     });

@@ -1324,6 +1324,25 @@ export class SingleSessionHTTPServer {         const hasUrl = headers['x-n8n-url'];         const hasKey = headers['x-n8n-key']; +        // SECURITY (GHSA-jxx9-px88-pj69): in multi-tenant mode, both headers+        // must be present. Falling through with no context would silently use+        // the operator's process-level N8N_API_KEY for the tenant's request.+        if (process.env.ENABLE_MULTI_TENANT === 'true' && !hasUrl && !hasKey) {+          logger.warn('Multi-tenant request missing tenant headers', {+            hasUrl: false,+            hasKey: false

+          });+          res.status(400).json({+            jsonrpc: '2.0',+            error: {+              code: -32602,+              message: 'Multi-tenant headers required'+            },+            id: req.body?.id ?? null+          });+          return;+        }+         if (hasUrl || hasKey) {           // Create context with proper type handling           const candidate: InstanceContext = {