Concrete CMS 9 through 9.5.2 is vulnerable to Missing Authorization in the orphaned-block alias route, allowing an authenticated editor to disclose and force-delete arbitrary blocks

{
  "id": "47c8006df517343419a92ff75e3cfc49ff912460bea4df11a8d99f0fe826fa70",
  "url": "https://osv.dev/vulnerability/CVE-2026-81909",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Concrete CMS 9 through 9.5.2 is vulnerable to Missing Authorization in the orphaned-block alias route, allowing an authenticated editor to disclose and force-delete arbitrary blocks",
    "summary": "Concrete CMS 9 through 9.5.2 is vulnerable to Missing Authorization in the block alias route (Process::alias() in concrete/controllers/backend/block/process.php).It does not verify that the referenced block is genuinely orphaned on the target page, nor that the caller holds any permission over the source block. A user granted only an area-scoped add_block_to_area delegation on their own page can therefore pass any block ID on the site: the source block's content is duplicated into an area the rogue editor controls, disclosing that content, and the original block is then force-deleted in the same request, destroying arbitrary site content. The Concrete CMS security team gave this vulnerability a CVSS v4.0 score of 5.9 with vector CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:N/VC:N/VI:H/VA:H/SC:N/SI:N/SA:N. Thanks Yonatan Drori from Tenzai for reporting.",
    "evidence": "osv:CVE-2026-81909",
    "products": [],
    "severity": "medium",
    "structured": {
      "id": "CVE-2026-81909",
      "aliases": [
        "CVE-2026-81909"
      ],
      "metrics": [
        {
          "type": "CVSS_V4",
          "score": "CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:N/VC:N/VI:H/VA:H/SC:N/SI:N/SA:N"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/concretecms/concretecms",
              "type": "GIT",
              "events": [
                {
                  "introduced": "b3774abddd475b4ba98b637402506f7a5ebd90ea"
                },
                {
                  "last_affected": "8fe9708072c3815a5df719b592e4b23b43b4ff7a"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "9.0.0"
                      },
                      {
                        "last_affected": "9.5.2"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StandardRange"
                  }
                ]
              }
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-81909.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:50.537956673Z",
      "provider": "osv",
      "references": [
        "https://documentation.concretecms.org/developers/introduction/version-history/953-release-notes",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/81xxx/CVE-2026-81909.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-81909",
        "https://github.com/concretecms/concretecms"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-862"
        ],
        "cna_assigner": "ConcreteCMS",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/81xxx/CVE-2026-81909.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-81909",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 518926,
  "published_at": "2026-09-11T17:49:47.885+00:00"
}