Nextcloud Calendar app allowed booking appointments without the generated token

{
  "id": "11567359f354c57a0eaaac20a4eaf5f4c62a4391c62ee20129abee8d6cc3a89c",
  "url": "https://osv.dev/vulnerability/CVE-2025-66546",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Nextcloud Calendar app allowed booking appointments without the generated token",
    "summary": "Nextcloud Calendar is a calendar app for Nextcloud. Prior to 4.7.19, 5.5.6, and 6.0.1, the calendar app allowed blindly booking appointments with a squential ID without known the appointment token. This vulnerability is fixed in 4.7.19, 5.5.6, and 6.0.1.",
    "evidence": "osv:CVE-2025-66546",
    "products": [],
    "severity": "low",
    "structured": {
      "id": "CVE-2025-66546",
      "aliases": [
        "CVE-2025-66546",
        "GHSA-7x2j-2674-fj95"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/nextcloud/calendar",
              "type": "GIT",
              "events": [
                {
                  "introduced": "d840d46412d121c9ae2697efed7f1ce6dd414fc2"
                },
                {
                  "fixed": "ee0fc1397f2cbade31712e17cabe7fd4503d3a32"
                },
                {
                  "introduced": "31203fddf125223d25f3b8b0d520f567a998e8af"
                },
                {
                  "fixed": "dfb76536948a4829539a61aaaa4d939afd743cb5"
                },
                {
                  "introduced": "d8566e7d4dffaec2a2c4a3adcdb0be9dab2556ba"
                },
                {
                  "fixed": "f41650c3681fc4a4130eb883f5c0899c011326b3"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "cpe": "cpe:2.3:a:nextcloud:calendar:*:*:*:*:*:*:*:*",
                    "range": [
                      {
                        "introduced": "4.0.0"
                      },
                      {
                        "fixed": "4.7.19"
                      }
                    ],
                    "source": "CPE_RANGE"
                  },
                  {
                    "cpe": "cpe:2.3:a:nextcloud:calendar:*:*:*:*:*:*:*:*",
                    "range": [
                      {
                        "introduced": "5.0.0"
                      },
                      {
                        "fixed": "5.5.6"
                      }
                    ],
                    "source": "CPE_RANGE"
                  },
                  {
                    "cpe": "cpe:2.3:a:nextcloud:calendar:6.0.0:-:*:*:*:*:*:*",
                    "range": [
                      {
                        "introduced": "6.0.0-NA"
                      },
                      {
                        "last_affected": "6.0.0-NA"
                      }
                    ],
                    "source": "CPE_STRING"
                  },
                  {
                    "range": [
                      {
                        "fixed": "f41650c3681fc4a4130eb883f5c0899c011326b3"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  }
                ]
              }
            }
          ],
          "versions": [
            "6.0.0-NA"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2025-66546.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:39.849603911Z",
      "provider": "osv",
      "references": [
        "https://hackerone.com/reports/3275810",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/66xxx/CVE-2025-66546.json",
        "https://github.com/nextcloud/security-advisories/security/advisories/GHSA-7x2j-2674-fj95",
        "https://nvd.nist.gov/vuln/detail/CVE-2025-66546",
        "https://github.com/nextcloud/calendar/commit/f41650c3681fc4a4130eb883f5c0899c011326b3",
        "https://github.com/nextcloud/calendar/pull/7537"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-639"
        ],
        "cna_assigner": "GitHub_M",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/66xxx/CVE-2025-66546.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2025-66546",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 507347,
  "published_at": "2025-12-05T16:49:46.553+00:00"
}