CVE-2026-53537

{
  "id": "CVE-2026-53537",
  "sourceIdentifier": "[email protected]",
  "published": "2026-06-22T18:16:44.077",
  "lastModified": "2026-10-25T23:10:00.167",
  "vulnStatus": "Analyzed",
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "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."
    },
    {
      "lang": "es",
      "value": "Python-Multipart es un analizador multipart de streaming para Python. Antes de la versión 0.0.30, parse_options_header analizaba los encabezados Content-Disposition (y Content-Type) con email.message.Message, que aplica de forma transparente la decodificación RFC 2231/5987. La sintaxis de parámetro extendida (filename=charset’lang’value, name=..., y la forma de continuación filename0/filename1) se decodifica y se expone bajo la clave filename/name simple, y anula el parámetro simple cuando ambos están presentes. RFC 7578 §4.2 prohíbe explícitamente la forma filename en multipart/form-data. Los componentes que siguen RFC 7578, o que no implementan la decodificación RFC 2231/5987 para multipart/form-data (WAFs, proxies, gateways), pueden interpretar dicho encabezado de manera diferente. Un atacante puede explotar esa diferencia para introducir un nombre de campo o nombre de archivo diferente más allá de un inspector ascendente hacia el backend. Esta vulnerabilidad está corregida en la versión 0.0.30."
    }
  ],
  "affected": [
    {
      "source": "[email protected]",
      "affectedData": [
        {
          "vendor": "Kludex",
          "product": "python-multipart",
          "versions": [
            {
              "version": "< 0.0.30",
              "status": "affected"
            }
          ]
        }
      ]
    }
  ],
  "metrics": {
    "cvssMetricV31": [
      {
        "source": "[email protected]",
        "type": "Secondary",
        "cvssData": {
          "version": "3.1",
          "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N",
          "baseScore": 3.7,
          "baseSeverity": "LOW",
          "attackVector": "NETWORK",
          "attackComplexity": "HIGH",
          "privilegesRequired": "NONE",
          "userInteraction": "NONE",
          "scope": "UNCHANGED",
          "confidentialityImpact": "NONE",
          "integrityImpact": "LOW",
          "availabilityImpact": "NONE"
        },
        "exploitabilityScore": 2.2,
        "impactScore": 1.4
      },
      {
        "source": "[email protected]",
        "type": "Primary",
        "cvssData": {
          "version": "3.1",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N",
          "baseScore": 5.3,
          "baseSeverity": "MEDIUM",
          "attackVector": "NETWORK",
          "attackComplexity": "LOW",
          "privilegesRequired": "NONE",
          "userInteraction": "NONE",
          "scope": "UNCHANGED",
          "confidentialityImpact": "NONE",
          "integrityImpact": "LOW",
          "availabilityImpact": "NONE"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 1.4
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "timestamp": "2026-06-23T16:03:15.384645Z",
          "id": "CVE-2026-53537",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "role": "CISA Coordinator",
          "version": "2.0.3"
        }
      }
    ]
  },
  "weaknesses": [
    {
      "source": "[email protected]",
      "type": "Secondary",
      "description": [
        {
          "lang": "en",
          "value": "CWE-20"
        },
        {
          "lang": "en",
          "value": "CWE-436"
        }
      ]
    }
  ],
  "configurations": [
    {
      "nodes": [
        {
          "operator": "OR",
          "negate": false,
          "cpeMatch": [
            {
              "vulnerable": true,
              "criteria": "cpe:2.3:a:fastapiexpert:python-multipart:*:*:*:*:*:python:*:*",
              "versionEndExcluding": "0.0.30",
              "matchCriteriaId": "381A8F1D-278D-409F-974A-898BE65DB20C"
            }
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  ],
  "references": [
    {
      "url": "https://github.com/Kludex/python-multipart/security/advisories/GHSA-vffw-93wf-4j4q",
      "source": "[email protected]",
      "tags": [
        "Vendor Advisory"
      ]
    }
  ]
}