id: CVE-2026-55605

info:
  name: "DeepSeek MCP Server - Missing Authentication on /mcp"
  author: vedas-arpsyndicate
  severity: medium
  description: |
    The self-hosted HTTP transport of @arikusi/deepseek-mcp-server from 1.4.2 before 1.8.0 exposes
    POST /mcp with no authentication: createMcpExpressApp is called without an authProvider and no
    middleware guards the route, so any network-reachable client can complete an MCP initialize
    handshake and obtain a session with no credentials. This template sends an unauthenticated
    JSON-RPC initialize request and confirms the server returns a valid MCP initialize result.
  reference:
    - https://www.exploit.observer/?keyword=CVE-2026-55605&match=exact
    - https://subdomain.center/?engine=ammonites&keyword=deepseek&match=exact
  classification:
    cvss-metrics: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
    cvss-score: 5.3
    cve-id: CVE-2026-55605
    cwe-id: CWE-306
  metadata:
    verified: false
  tags: cve,cve2026,deepseek,mcp,auth-bypass

http:
  - raw:
      - |
        POST /mcp HTTP/1.1
        Host: {{Hostname}}
        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":"vedas-check","version":"1.0"}}}

    matchers-condition: and
    matchers:
      - type: status
        status:
          - 200
      - type: word
        part: body
        words:
          - '"protocolVersion"'
          - '"serverInfo"'
        condition: and