{
  "affected": [
    {
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "885ddcc33cf9657caf38c57c7be45ae1c5272802"
            }
          ],
          "repo": "https://github.com/webreflection/flatted",
          "type": "GIT"
        },
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "3bf09091c3562e17a0647bc06710dd6097079cf7"
            }
          ],
          "repo": "https://github.com/webreflection/flatted",
          "type": "GIT"
        }
      ]
    }
  ],
  "aliases": [
    "GHSA-rf6f-7fwh-wjgh"
  ],
  "database_specific": {
    "cna_assigner": "GitHub_M",
    "cwe_ids": [
      "CWE-1321"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/33xxx/CVE-2026-33228.json"
  },
  "details": "flatted is a circular JSON parser. Prior to version 3.4.2, the parse() function in flatted can use attacker-controlled string values from the parsed JSON as direct array index keys, without validating that they are numeric. Since the internal input buffer is a JavaScript Array, accessing it with the key \"__proto__\" returns Array.prototype via the inherited getter. This object is then treated as a legitimate parsed value and assigned as a property of the output object, effectively leaking a live reference to Array.prototype to the consumer. Any code that subsequently writes to that property will pollute the global prototype. This issue has been patched in version 3.4.2.",
  "id": "CVE-2026-33228",
  "modified": "2026-04-01T23:08:23.775297278Z",
  "published": "2026-03-20T23:06:48.485Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/WebReflection/flatted/releases/tag/v3.4.2"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/33xxx/CVE-2026-33228.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/WebReflection/flatted/security/advisories/GHSA-rf6f-7fwh-wjgh"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-33228"
    },
    {
      "type": "FIX",
      "url": "https://github.com/WebReflection/flatted/commit/885ddcc33cf9657caf38c57c7be45ae1c5272802"
    }
  ],
  "schema_version": "1.7.3",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:P",
      "type": "CVSS_V4"
    }
  ],
  "summary": "flatted: Prototype Pollution via parse()"
}