{
  "affected": [
    {
      "package": {
        "ecosystem": "npm",
        "name": "hono"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "4.12.7"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [],
  "database_specific": {
    "cwe_ids": [
      "CWE-1321"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-03-11T00:31:47Z",
    "nvd_published_at": null,
    "severity": "MODERATE"
  },
  "details": "## Summary\n\nWhen using `parseBody({ dot: true })` in HonoRequest, specially crafted form field names such as `__proto__.x` could create objects containing a `__proto__` property.\n\nIf the parsed result is later merged into regular JavaScript objects using unsafe merge patterns, this may lead to prototype pollution in the target object.\n\n## Details\n\nThe `parseBody({ dot: true })` feature supports dot notation to construct nested objects from form field names.\n\nIn previous versions, the `__proto__` path segment was not filtered. As a result, specially crafted keys such as `__proto__.x` could produce objects containing `__proto__` properties.\n\nWhile this behavior does not directly modify `Object.prototype` within Hono itself, it may become exploitable if the parsed result is later merged into regular JavaScript objects using unsafe merge patterns.\n\n## Impact\n\nApplications that merge parsed form data into regular objects using unsafe patterns (for example recursive deep merge utilities) may become vulnerable to prototype pollution.",
  "id": "GHSA-v8w9-8mx6-g223",
  "modified": "2026-03-11T00:31:47Z",
  "published": "2026-03-11T00:31:47Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/honojs/hono/security/advisories/GHSA-v8w9-8mx6-g223"
    },
    {
      "type": "WEB",
      "url": "https://github.com/honojs/hono/commit/ef902257e0beacbb83d2a9549b3b83e03514a6fe"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/honojs/hono"
    }
  ],
  "schema_version": "1.4.0",
  "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": "Hono vulnerable to Prototype Pollution possible through __proto__ key allowed in parseBody({ dot: true })"
}