{
  "affected": [
    {
      "ranges": [
        {
          "database_specific": {
            "cpe": "cpe:2.3:a:fastapiexpert:python-multipart:*:*:*:*:*:python:*:*",
            "extracted_events": [
              {
                "introduced": "0"
              },
              {
                "fixed": "0.0.30"
              }
            ],
            "source": [
              "AFFECTED_FIELD",
              "CPE_RANGE"
            ]
          },
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "9d3ead568a259f222cff6425262ff63e88d930d4"
            }
          ],
          "repo": "https://github.com/kludex/python-multipart",
          "type": "GIT"
        }
      ]
    }
  ],
  "aliases": [
    "GHSA-vffw-93wf-4j4q"
  ],
  "database_specific": {
    "cna_assigner": "GitHub_M",
    "cwe_ids": [
      "CWE-20",
      "CWE-436"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/53xxx/CVE-2026-53537.json"
  },
  "details": "Python-Multipart is a streaming multipart parser for Python. Prior to 0.0.30, parse_options_header parsed Content-Disposition (and Content-Type) headers with email.message.Message, which transparently applies RFC 2231/5987 decoding. The extended parameter syntax (filename*=charset'lang'value, name*=..., and the filename*0/filename*1 continuation form) is decoded and surfaced under the bare filename/name key, and overrides the plain parameter when both are present. RFC 7578 §4.2 explicitly forbids the filename* form in multipart/form-data. Components that follow RFC 7578, or that do not implement RFC 2231/5987 decoding for multipart/form-data (WAFs, proxies, gateways), may interpret such a header differently. An attacker can exploit that difference to smuggle a different field name or filename past an upstream inspector to the backend. This vulnerability is fixed in 0.0.30.",
  "id": "CVE-2026-53537",
  "modified": "2026-07-08T05:37:49.270660016Z",
  "published": "2026-06-22T16:57:21.496Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/53xxx/CVE-2026-53537.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/Kludex/python-multipart/security/advisories/GHSA-vffw-93wf-4j4q"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-53537"
    }
  ],
  "schema_version": "1.7.5",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Python-Multipart: Content-Disposition parameter smuggling via RFC 2231/5987 extended parameters"
}