diff --git a/src/__tests__/cors-fix.test.ts b/src/__tests__/cors-fix.test.ts
new file mode 100644
index 0000000..f4d67e7
--- /dev/null
+++ b/src/__tests__/cors-fix.test.ts
@@ -0,0 +1,26 @@
+import { describe, it, expect } from 'vitest';
+import { readFileSync } from 'fs';
+import { join, dirname } from 'path';
+import { fileURLToPath } from 'url';
+
+const __dirname = dirname(fileURLToPath(import.meta.url));
+
+describe('CWE-346 CORS fix in server.ts', () => {
+  const src = readFileSync(join(__dirname, '..', 'server.ts'), 'utf8');
+
+  it('does not reflect Origin header back into Access-Control-Allow-Origin', () => {
+    expect(src).not.toMatch(/Access-Control-Allow-Origin['"]\s*,\s*origin\b/);
+  });
+
+  it('uses a static wildcard for Access-Control-Allow-Origin', () => {
+    expect(src).toMatch(/Access-Control-Allow-Origin['"]\s*,\s*['"]\*['"]/);
+  });
+
+  it('does not enable Access-Control-Allow-Credentials', () => {
+    expect(src).not.toMatch(/Access-Control-Allow-Credentials/);
+  });
+
+  it('includes a DNS-rebinding Origin/Host check', () => {
+    expect(src).toMatch(/DNS rebinding protection/i);
+  });
+});
diff --git a/src/server.ts b/src/server.ts
index 4319e3a..148303a 100644
--- a/src/server.ts
+++ b/src/server.ts
@@ -192,11 +192,12 @@ See documentation for more details on configuring database connections.
           }
         }
 
-        // CORS headers — only reflect validated origins
-        res.header('Access-Control-Allow-Origin', origin || 'http://localhost');
+        // CORS headers: use a static wildcard origin and do not enable
+        // cross-origin credentials. The co-hosted workbench uses same-origin
+        // requests, so credentialed CORS is not required.
+        res.header('Access-Control-Allow-Origin', '*');
         res.header('Access-Control-Allow-Methods', 'GET, POST, OPTIONS');
         res.header('Access-Control-Allow-Headers', 'Content-Type, Mcp-Session-Id');
-        res.header('Access-Control-Allow-Credentials', 'true');
 
         if (req.method === 'OPTIONS') {
           return res.sendStatus(200);