{
  "affected": [
    {
      "ranges": [
        {
          "events": [
            {
              "introduced": "2b27bd81899d8607f82ad41c2831bef91db835a5"
            },
            {
              "fixed": "3ff24f81b96792d96a2647d7b1f857b891c84643"
            }
          ],
          "repo": "https://github.com/nextcloud/user_oidc",
          "type": "GIT"
        }
      ]
    }
  ],
  "aliases": [
    "GHSA-xx3h-v363-q36j"
  ],
  "database_specific": {
    "cna_assigner": "GitHub_M",
    "cwe_ids": [
      "CWE-303"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2023/39xxx/CVE-2023-39953.json"
  },
  "details": "user_oidc provides the OIDC connect user backend for Nextcloud, an open-source cloud platform. Starting in version 1.0.0 and prior to version 1.3.3, missing verification of the issuer would have allowed an attacker to perform a man-in-the-middle attack returning corrupted or known token they also have access to. user_oidc 1.3.3 contains a patch. No known workarounds are available.",
  "id": "CVE-2023-39953",
  "modified": "2026-04-01T23:07:59.205335765Z",
  "published": "2023-08-10T13:55:19.957Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://hackerone.com/reports/2021684"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2023/39xxx/CVE-2023-39953.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/nextcloud/security-advisories/security/advisories/GHSA-xx3h-v363-q36j"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2023-39953"
    },
    {
      "type": "FIX",
      "url": "https://github.com/nextcloud/user_oidc/pull/642"
    }
  ],
  "schema_version": "1.7.3",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Issuer not verified from obtained token in user_oidc"
}