CVE-2026-55605

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

MEDIUM

5.3

CVSS Score

Published: July 9, 2026 at 09:10 PM UTC

Updated: October 25, 2026 at 05:10 PM UTC

1 product affected across 1 vendorDeepSeek MCP Server

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Severity

MEDIUM5.3

Exploit prediction

EPSS 0.5%

SSVC

PoC

Description

DeepSeek MCP Server is an MCP server for DeepSeek V4. Starting in version 1.4.2 and prior to version 1.8.0, 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`). Version 1.8.0 contains a patch for this issue.