rules:
  - id: auth.mcp.dns-rebinding-unprotected
    languages:
      - javascript
      - typescript
    severity: ERROR
    message: |
      This MCP `StreamableHTTPServerTransport` is created without DNS-rebinding
      protection (CWE-346). `enableDnsRebindingProtection` defaults to `false`
      in the TypeScript SDK, so a malicious web page the user visits can rebind
      a DNS name to the loopback address and POST to the local MCP server,
      driving its tools cross-origin from the browser. This is CVE-2025-66416.

      Enable it and pin the Host/Origin allow-lists:
        new StreamableHTTPServerTransport({
          sessionIdGenerator: () => randomUUID(),
          enableDnsRebindingProtection: true,
          allowedHosts: ['127.0.0.1:3000'],
          allowedOrigins: ['https://app.example.com'],
        })
    # Fires when the transport is constructed WITHOUT `enableDnsRebindingProtection:
    # true`. `pattern-not` subtracts the explicitly-enabled form, so a hardened
    # transport (or one that sets it true) does NOT trip; absent-or-false trips.
    patterns:
      - pattern: new StreamableHTTPServerTransport({...})
      - pattern-not: 'new StreamableHTTPServerTransport({..., enableDnsRebindingProtection: true, ...})'
    metadata:
      oauthlint-rule-id: AUTH-MCP-005
      oauthlint-doc-url: https://oauthlint.dev/rules/mcp-dns-rebinding-unprotected
      category: security
      cwe: CWE-346
      owasp: API8:2023
      llm-prevalence: HIGH
      technology:
        - mcp
        - modelcontextprotocol
      references:
        - https://modelcontextprotocol.io/specification/2026-07-28/basic/authorization
        - https://www.cve.org/CVERecord?id=CVE-2025-66416
        - https://cwe.mitre.org/data/definitions/346.html