{
  "affected": [
    {
      "ranges": [
        {
          "database_specific": {
            "cpe": "cpe:2.3:a:ultrajson_project:ultrajson:*:*:*:*:*:python:*:*",
            "extracted_events": [
              {
                "introduced": "0"
              },
              {
                "fixed": "5.13.0"
              }
            ],
            "source": [
              "CPE_RANGE",
              "REFERENCES"
            ]
          },
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1a23a68bbc5aff84e3f78f65011362cf3389693c"
            },
            {
              "fixed": "169eaf36b1116fece5034ee79a7a0ef3f6deedcf"
            }
          ],
          "repo": "https://github.com/ultrajson/ultrajson",
          "type": "GIT"
        }
      ]
    }
  ],
  "aliases": [
    "GHSA-3j69-69wj-xqx2"
  ],
  "database_specific": {
    "cna_assigner": "GitHub_M",
    "cwe_ids": [
      "CWE-20"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/54xxx/CVE-2026-54911.json"
  },
  "details": "UltraJSON is a fast JSON encoder and decoder written in pure C with bindings for Python 3.7+. Prior to 5.13.0, ujson.dumps() (or ujson.dump() or ujson.encode()) have a reject_bytes=False option. When set, they may accept malformed or truncated UTF-8 byte sequences, silently rewriting them into different Unicode characters instead of rejecting them. This leads to input validation bypass and data integrity issues. This vulnerability is fixed in 5.13.0.",
  "id": "CVE-2026-54911",
  "modified": "2026-07-15T01:48:51.642336351Z",
  "published": "2026-06-22T20:53:07.019Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/ultrajson/ultrajson/releases/tag/5.13.0"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/54xxx/CVE-2026-54911.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/ultrajson/ultrajson/security/advisories/GHSA-3j69-69wj-xqx2"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-54911"
    },
    {
      "type": "FIX",
      "url": "https://github.com/ultrajson/ultrajson/commit/169eaf36b1116fece5034ee79a7a0ef3f6deedcf"
    }
  ],
  "schema_version": "1.8.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "UltraJSON: Malformed/Truncated UTF-8 Accepted and Silently Rewritten in ujson.dumps()"
}