id: CVE-2026-77339

info:
  name: "Process Compose - MCP SSE Listener Missing Origin/Host Validation"
  author: vedas-arpsyndicate
  severity: high
  description: |
    Process Compose prior to 1.120.0 exposes its MCP Server-Sent Events listener at GET /sse
    without validating the Host or Origin header and without authenticating the caller. The
    separately started MCP listener is not protected by the Gin REST API token middleware, so a
    cross-origin browser request receives the SSE endpoint event and an Access-Control-Allow-Origin
    wildcard, enabling DNS-rebinding attacks that can enumerate and control local processes. This
    template sends an unauthenticated cross-origin GET to /sse and confirms the listener returns the
    SSE event stream with a wildcard CORS header, proving the missing origin/authentication controls.
  reference:
    - https://www.exploit.observer/?keyword=CVE-2026-77339&match=exact
    - https://subdomain.center/?engine=ammonites&keyword=process-compose&match=exact
  classification:
    cve-id: CVE-2026-77339
    cwe-id: CWE-346
  metadata:
    verified: false
    max-request: 1
  tags: cve,cve2026,process-compose,mcp,sse,dns-rebinding,auth-bypass

http:
  - raw:
      - |
        GET /sse HTTP/1.1
        Host: {{Hostname}}
        Accept: text/event-stream
        Origin: https://evil.example

    matchers-condition: and
    matchers:
      - type: status
        status:
          - 200
      - type: word
        part: header
        words:
          - "text/event-stream"
          - "Access-Control-Allow-Origin: *"
        condition: and
      - type: word
        part: body
        words:
          - "sessionId="