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CVE-2021-33503

Estado: ModificadaAlta (7.5)—

An issue was discovered in urllib3 before 1.26.5. When provided with a URL containing many @ characters in the authority component, the authority regular expression exhibits catastrophic backtracking, causing a denial of service if a URL were passed as a parameter or redirected to via an HTTP redirect.

CVSS

Probabilidad de explotación (EPSS)

EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).

Tecnologías afectadas (5)

Fedoraproject — FedoraOracle — Enterprise Manager OPS CenterOracle — Instantis EnterprisetrackOracle — ZFS Storage Appliance KITPython — Urllib3

CWE

Referencias

JSON original (NVD)

Mostrar
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  "id": "CVE-2021-33503",
  "cveTags": [],
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          "accessVector": "NETWORK",
          "vectorString": "AV:N/AC:L/Au:N/C:N/I:N/A:P",
          "authentication": "NONE",
          "integrityImpact": "NONE",
          "accessComplexity": "LOW",
          "availabilityImpact": "PARTIAL",
          "confidentialityImpact": "NONE"
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        "impactScore": 2.9,
        "baseSeverity": "MEDIUM",
        "obtainAllPrivilege": false,
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          "baseSeverity": "HIGH",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
          "integrityImpact": "NONE",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "availabilityImpact": "HIGH",
          "privilegesRequired": "NONE",
          "confidentialityImpact": "NONE"
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        "impactScore": 3.6,
        "exploitabilityScore": 3.9
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  "affected": [
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      "affectedData": [
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          "versions": [
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  "published": "2021-06-29T11:15:07.847",
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  "vulnStatus": "Modified",
  "weaknesses": [
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          "value": "CWE-400"
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      "value": "An issue was discovered in urllib3 before 1.26.5. When provided with a URL containing many @ characters in the authority component, the authority regular expression exhibits catastrophic backtracking, causing a denial of service if a URL were passed as a parameter or redirected to via an HTTP redirect."
    },
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      "lang": "es",
      "value": "Se ha detectado un problema en urllib3 versiones anteriores a 1.26.5. Cuando se proporciona una URL que contiene muchos caracteres @ en el componente authority, la expresión regular de autoridad muestra un retroceso catastrófico, causando una denegación de servicio si fue pasado una URL como parámetro o es redirigido a ella por medio de un redireccionamiento HTTP"
    }
  ],
  "lastModified": "2026-06-17T03:54:41.387",
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