{
  "affected": [
    {
      "ranges": [
        {
          "database_specific": {
            "extracted_events": [
              {
                "introduced": "8.2.0"
              },
              {
                "fixed": "8.6.5"
              }
            ],
            "source": [
              "AFFECTED_FIELD",
              "REFERENCES"
            ]
          },
          "events": [
            {
              "introduced": "f8d5f3fe7104fade45407341228f0f0bb623e76d"
            },
            {
              "fixed": "9f97fe413072d3beb52c74e62d88ea8adc9444d8"
            },
            {
              "fixed": "3f7b2fa2dd679f7099a30098a75bcd776615e86f"
            }
          ],
          "repo": "https://github.com/protobufjs/protobuf.js",
          "type": "GIT"
        }
      ]
    }
  ],
  "aliases": [
    "GHSA-jfj6-75fj-8934"
  ],
  "database_specific": {
    "cna_assigner": "GitHub_M",
    "cwe_ids": [
      "CWE-1321"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/59xxx/CVE-2026-59876.json"
  },
  "details": "protobufjs compiles protobuf definitions into JavaScript (JS) functions. From 8.2.0 until 8.6.5, the protobufjs Text Format extension parsed string-keyed map entries using ordinary property assignment, allowing a map entry with key __proto__ to change the prototype of the returned map object instead of creating an own map entry in protobufjs/ext/textformat. This issue is fixed in version 8.6.5.",
  "id": "CVE-2026-59876",
  "modified": "2026-07-15T01:49:22.536654570Z",
  "published": "2026-07-08T15:31:11.421Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/protobufjs/protobuf.js/releases/tag/protobufjs-v8.6.5"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/59xxx/CVE-2026-59876.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/protobufjs/protobuf.js/security/advisories/GHSA-jfj6-75fj-8934"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-59876"
    },
    {
      "type": "FIX",
      "url": "https://github.com/protobufjs/protobuf.js/commit/9f97fe413072d3beb52c74e62d88ea8adc9444d8"
    },
    {
      "type": "FIX",
      "url": "https://github.com/protobufjs/protobuf.js/pull/2335"
    }
  ],
  "schema_version": "1.8.0",
  "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": "protobufjs: Text Format string map parsing can mutate returned map object prototype"
}