{
  "affected": [
    {
      "ranges": [
        {
          "events": [
            {
              "introduced": "9593648d4289e262035821179e73f16a3271dee9"
            },
            {
              "fixed": "428b9765af69739897b86c294563af8809dd40c3"
            }
          ],
          "repo": "https://github.com/elysiajs/elysia",
          "type": "GIT"
        }
      ]
    }
  ],
  "database_specific": {
    "cna_assigner": "GitHub_M",
    "cwe_ids": [
      "CWE-1321"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/66xxx/CVE-2025-66456.json"
  },
  "details": "Elysia is a Typescript framework for request validation, type inference, OpenAPI documentation and client-server communication. Versions 1.4.0 through 1.4.16 contain a prototype pollution vulnerability in `mergeDeep` after merging results of two standard schema validations with the same key. Due to the ordering of merging, there must be an any type that is set as a standalone guard, to allow for the `__proto__ prop` to be merged. When combined with GHSA-8vch-m3f4-q8jf this allows for a full RCE by an attacker. This issue is fixed in version 1.4.17. To workaround, remove the `__proto__ key` from body.",
  "id": "CVE-2025-66456",
  "modified": "2026-04-01T23:10:08.065528676Z",
  "published": "2025-12-09T19:43:10.252Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/66xxx/CVE-2025-66456.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/elysiajs/elysia/security/advisories/GHSA-8vch-m3f4-q8jf"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/elysiajs/elysia/security/advisories/GHSA-hxj9-33pp-j2cc"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2025-66456"
    },
    {
      "type": "FIX",
      "url": "https://github.com/elysiajs/elysia/commit/26935bf76ebc43b4a43d48b173fc853de43bb51e"
    },
    {
      "type": "FIX",
      "url": "https://github.com/elysiajs/elysia/commit/3af978663e437dccc6c1a2a3aff4b74e1574849e"
    },
    {
      "type": "FIX",
      "url": "https://github.com/elysiajs/elysia/pull/1564"
    }
  ],
  "related": [
    "GHSA-8vch-m3f4-q8jf",
    "GHSA-hxj9-33pp-j2cc"
  ],
  "schema_version": "1.7.3",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Elysia vulnerable to prototype pollution with multiple standalone schema validation"
}