Easy!Appointments: Authorization bypass in Google OAuth provider binding lets any backend user rebind a peer provider's Google sync

{
  "id": "c639445300287c017af62d84a7b0180dda9653f288c8b889570887b0540fc334",
  "url": "https://osv.dev/vulnerability/CVE-2026-52841",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Easy!Appointments: Authorization bypass in Google OAuth provider binding lets any backend user rebind a peer provider's Google sync",
    "summary": "Easy!Appointments is a self hosted appointment scheduler. In versions prior to 1.6.0, `Google::oauth` at `application/controllers/Google.php:278` stores its URL-supplied `provider_id` in the session, and `oauth_callback` saves the issued Google OAuth token against that row without checking the caller owns the provider. Any logged-in backend user (admin, provider, or secretary) rebinds a peer provider's Google sync to a Google account they control. The peer's appointments then sync into the attacker's calendar with each customer's name and email attached as attendee data. Version 1.6.0 patches the issue.",
    "evidence": "osv:CVE-2026-52841",
    "products": [],
    "severity": "low",
    "structured": {
      "id": "CVE-2026-52841",
      "aliases": [
        "CVE-2026-52841",
        "GHSA-8hm4-r66f-29wr"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:H/PR:H/UI:R/S:U/C:L/I:L/A:N"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/alextselegidis/easyappointments",
              "type": "GIT",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "4bc7ecd51f3dade8e041558f2c23dda65bd6c43e"
                },
                {
                  "fixed": "4b2d245d2cd2058dc76e05f6eb65b26699268471"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "fixed": "1.6.0"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StringRangeExpression"
                  },
                  {
                    "range": [
                      {
                        "fixed": "4b2d245d2cd2058dc76e05f6eb65b26699268471"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  }
                ]
              }
            }
          ],
          "versions": [
            "1.6.0-beta.2",
            "1.6.0-beta.1",
            "1.6.0-alpha.1",
            "1.5.2-beta.1",
            "1.5.1",
            "1.5.1-beta.1",
            "1.5.0",
            "1.5.0-beta.1",
            "1.5.0-alpha.1",
            "1.5.0-dev.4",
            "1.5.0-dev.3",
            "1.5.0-dev.2",
            "1.5.0-dev.1",
            "1.3.0-beta.2",
            "1.3.0-beta.1",
            "1.3.0-alpha.1",
            "1.2.0-beta.1",
            "1.2.0-alpha.1",
            "1.1.0",
            "1.1.0-beta.2"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-52841.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:29.355077104Z",
      "provider": "osv",
      "references": [
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/52xxx/CVE-2026-52841.json",
        "https://github.com/alextselegidis/easyappointments/security/advisories/GHSA-8hm4-r66f-29wr",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-52841",
        "https://github.com/alextselegidis/easyappointments/commit/4b2d245d2cd2058dc76e05f6eb65b26699268471"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-639"
        ],
        "cna_assigner": "GitHub_M",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/52xxx/CVE-2026-52841.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-52841",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 496340,
  "published_at": "2026-07-14T15:27:50.367+00:00"
}