CVE-2026-55605

## Summary The self-hosted HTTP transport of `@arikusi/deepseek-mcp-server` exposes `POST /mcp` without any authentication: `createMcpExpressApp` is called without an `authProvider` and no middleware guards the route, so any network-reachable client can issue an unauthenticated `initialize` request and obtain a valid MCP session identifier. In reproduced testing against commit `5e1302171e99`, an unauthenticated client was able to initialize a session, enumerate tools, and invoke the local `deepseek_sessions` tool with no credentials. The same unauthenticated session also exposes `deepseek_chat`, whose handler uses the server-side `DEEPSEEK_API_KEY` when self-hosted deployments configure one. This issue applies to self-hosted HTTP mode, not the separately documented hosted BYOK endpoint in `README.md`, which expects an `Authorization: Bearer ...` header. Upstream self-hosted container assets enable HTTP mode by default (`Dockerfile`) and publish port `3000` (`docker-compose.yml`). ## Affected Code `src/transport-http.ts:17` — `createMcpExpressApp` called without `authProvider`; no challenge is issued to incoming requests ```typescript export function createHttpApp(serverFactory: () => McpServer) { const app = createMcpExpressApp({ host: '0.0.0.0' }); ``` `src/transport-http.ts:31` — `POST /mcp` handler instantiates a full MCP session for any body that satisfies `isInitializeRequest`, with no preceding auth check ```typescript app.post('/mcp', async (req, res) => { const sessionId = req.headers['mcp-session-id'] as string | undefined; if (sessionId && transports[sessionId]) { await transports[sessionId].handleRequest(req, res, req.body); return; } if (!sessionId && isInitializeRequest(req.body)) { const transport = new StreamableHTTPServerTransport({ sessionIdGenerator: () => randomUUID(), onsessioninitialized: (id) => { transports[id] = transport; console.error(`[DeepSeek MCP] HTTP sessi