Craft CMS: Authorship spoofing in `entries/save-entry` via pre-check/post-mutation authorization gap

{
  "id": "e408677ed81cc994dc9bf6a7afdde674b0d12f8c8f3bf2f7c424a7aefc916f70",
  "url": "https://osv.dev/vulnerability/CVE-2026-50279",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Craft CMS: Authorship spoofing in `entries/save-entry` via pre-check/post-mutation authorization gap",
    "summary": "Craft CMS is a content management system (CMS). IN versions 5.0.0-RC1 and above prior to 5.9.21, theEntriesController::actionSaveEntry() performs entry-edit permission checks before request-controlled author changes are applied to the model, allowing for authorship spoofing. The subsequent author mutation path accepts attacker-supplied authors / author parameters and allows the change when the current user is one of the old authors. Because the controller does not re-run authorization after mutating the author list, a low-privileged user can reassign an entry’s authorship to another user without holding the dedicated peer-author-change permission. This issue has been fixed in version 5.9.21.",
    "evidence": "osv:CVE-2026-50279",
    "products": [],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-50279",
      "aliases": [
        "CVE-2026-50279",
        "GHSA-qq2c-2q8j-jh27"
      ],
      "metrics": [
        {
          "type": "CVSS_V4",
          "score": "CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/craftcms/cms",
              "type": "GIT",
              "events": [
                {
                  "introduced": "04755d93f86d07cc183db47db8a0eee106892e30"
                },
                {
                  "fixed": "887cc875cf041f6d0ecc55c7a0a687c41b402a24"
                },
                {
                  "fixed": "9cc493be8b414d7116c7f2bc2a6d0926e73f1248"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "5.0.0-RC1"
                      },
                      {
                        "fixed": "5.9.21"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StringRangeExpression"
                  },
                  {
                    "range": [
                      {
                        "fixed": "9cc493be8b414d7116c7f2bc2a6d0926e73f1248"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  }
                ]
              }
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-50279.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:50.001426735Z",
      "provider": "osv",
      "references": [
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/50xxx/CVE-2026-50279.json",
        "https://github.com/craftcms/cms/security/advisories/GHSA-qq2c-2q8j-jh27",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-50279",
        "https://github.com/craftcms/cms/commit/9cc493be8b414d7116c7f2bc2a6d0926e73f1248"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-285"
        ],
        "cna_assigner": "GitHub_M",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/50xxx/CVE-2026-50279.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-50279",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 518564,
  "published_at": "2026-07-01T23:31:31.101+00:00"
}