{
  "affected": [
    {
      "ranges": [
        {
          "database_specific": {
            "extracted_events": [
              {
                "introduced": "0"
              },
              {
                "fixed": "2.3.1"
              }
            ],
            "source": [
              "AFFECTED_FIELD",
              "REFERENCES"
            ]
          },
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "94a2b7560b2b5ed903a4d466a3bce8b13daa2660"
            },
            {
              "fixed": "352a5b017d190cb01d6fc70e18fcaf06f9bbc6e5"
            }
          ],
          "repo": "https://github.com/toon-format/toon",
          "type": "GIT"
        }
      ]
    }
  ],
  "aliases": [
    "GHSA-p95v-992w-h6c3"
  ],
  "database_specific": {
    "cna_assigner": "GitHub_M",
    "cwe_ids": [
      "CWE-1321"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/82xxx/CVE-2026-82404.json"
  },
  "details": "TOON is a compact, human-readable serialization of JSON data for LLM prompts. Prior to 2.3.1, decoding attacker-controlled TOON with a __proto__, constructor, or prototype key wrote through the object prototype chain instead of creating an own property, polluting Object.prototype for the runtime. In packages/toon/src/decode/expand.ts, the expandPaths: 'safe' path and insertPathSafe function made dotted keys such as a.__proto__.x the strongest vector, while plain nested objects, tabular rows, quoted keys, and streaming decode were also affected. The encoder also dropped own __proto__ properties and could invoke an inherited setter during normalization. Services that decode untrusted TOON could experience denial of service or, when a suitable downstream gadget is present, remote code execution. This issue is fixed in version 2.3.1.",
  "id": "CVE-2026-82404",
  "modified": "2026-09-04T03:31:02.226788647Z",
  "published": "2026-09-02T16:30:54.876Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/toon-format/toon/releases/tag/v2.3.1"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/82xxx/CVE-2026-82404.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/toon-format/toon/security/advisories/GHSA-p95v-992w-h6c3"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-82404"
    },
    {
      "type": "FIX",
      "url": "https://github.com/toon-format/toon/commit/94a2b7560b2b5ed903a4d466a3bce8b13daa2660"
    },
    {
      "type": "FIX",
      "url": "https://github.com/toon-format/toon/pull/316"
    }
  ],
  "schema_version": "1.9.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:L",
      "type": "CVSS_V3"
    }
  ],
  "summary": "TOON: Prototype pollution when decoding untrusted TOON input"
}