{
  "affected": [
    {
      "affectedData": [
        {
          "product": "python-multipart",
          "vendor": "Kludex",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 0.0.30"
            }
          ]
        }
      ],
      "source": "security-advisories@github.com"
    }
  ],
  "configurations": [
    {
      "nodes": [
        {
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:a:fastapiexpert:python-multipart:*:*:*:*:*:python:*:*",
              "matchCriteriaId": "381A8F1D-278D-409F-974A-898BE65DB20C",
              "versionEndExcluding": "0.0.30",
              "vulnerable": true
            }
          ],
          "negate": false,
          "operator": "OR"
        }
      ]
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "Python-Multipart is a streaming multipart parser for Python. Prior to 0.0.30, when parsing application/x-www-form-urlencoded bodies, QuerystringParser located the field separator with a two step lookup: it first scanned the entire remaining buffer for \u0026, and only when no \u0026 existed anywhere ahead did it fall back to scanning for ;. For a body that uses ; as the separator and contains no \u0026, every field iteration performed a full failed \u0026 scan over the entire remaining buffer before locating the nearby ;. With N semicolon separated fields in a chunk of size B, this yields O(B^2) byte comparisons per chunk. An attacker can submit a small crafted body of the form a;a;a;... and cause the parser to spend seconds of CPU per request. A handful of concurrent requests can exhaust worker processes. This vulnerability is fixed in 0.0.30."
    },
    {
      "lang": "es",
      "value": "Python-Multipart es un analizador multipart de streaming para Python. Antes de la versi\u00f3n 0.0.30, al analizar cuerpos application/x-www-form-urlencoded, QuerystringParser localizaba el separador de campo con una b\u00fasqueda en dos pasos: primero escaneaba todo el b\u00fafer restante en busca de \u0026, y solo cuando no exist\u00eda ning\u00fan \u0026 m\u00e1s adelante, recurr\u00eda a escanear en busca de ;. Para un cuerpo que usa ; como separador y no contiene ning\u00fan \u0026, cada iteraci\u00f3n de campo realizaba un escaneo completo fallido de \u0026 sobre todo el b\u00fafer restante antes de localizar el ; cercano. Con N campos separados por punto y coma en un fragmento de tama\u00f1o B, esto produce O(B^2) comparaciones de bytes por fragmento. Un atacante puede enviar un cuerpo peque\u00f1o y manipulado de la forma a;a;a;... y hacer que el analizador gaste segundos de CPU por solicitud. Un pu\u00f1ado de solicitudes concurrentes puede agotar los procesos de trabajo. Esta vulnerabilidad est\u00e1 corregida en la versi\u00f3n 0.0.30."
    }
  ],
  "id": "CVE-2026-53539",
  "lastModified": "2026-10-25T23:10:00.167",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "HIGH",
          "baseScore": 7.5,
          "baseSeverity": "HIGH",
          "confidentialityImpact": "NONE",
          "integrityImpact": "NONE",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 3.6,
        "source": "security-advisories@github.com",
        "type": "Secondary"
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-53539",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "yes"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2026-06-23T14:05:50.901666Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2026-06-22T18:16:44.360",
  "references": [
    {
      "source": "security-advisories@github.com",
      "tags": [
        "Vendor Advisory"
      ],
      "url": "https://github.com/Kludex/python-multipart/security/advisories/GHSA-5rvq-cxj2-64vf"
    }
  ],
  "sourceIdentifier": "security-advisories@github.com",
  "vulnStatus": "Analyzed",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-400"
        },
        {
          "lang": "en",
          "value": "CWE-407"
        }
      ],
      "source": "security-advisories@github.com",
      "type": "Secondary"
    }
  ]
}