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  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "A HTTP/2 implementation built using any version of the Python HPACK library between v1.0.0 and v2.2.0 could be targeted for a denial of service attack, specifically a so-called \"HPACK Bomb\" attack. This attack occurs when an attacker inserts a header field that is exactly the size of the HPACK dynamic header table into the dynamic header table. The attacker can then send a header block that is simply repeated requests to expand that field in the dynamic table. This can lead to a gigantic compression ratio of 4,096 or better, meaning that 16kB of data can decompress to 64MB of data on the target machine."
    },
    {
      "lang": "es",
      "value": "Una implementaci\u00f3n de HTTP/2 construida usando cualquier versi\u00f3n de la librer\u00eda de Python HPACK entre las versiones v1.0.0 y v2.2.0 podr\u00eda ser atacada por un ataque de denegaci\u00f3n de servicio, especialmente un ataque llamado \"HPACK Bomb\". Este ataque ocurre cuando un atacante inserta un campo de cabecera que es exactamente del tama\u00f1o de la tabla de cabecera din\u00e1mica HPACK dentro de la tabla de cabecera din\u00e1mica. El atacante puede entonces enviar un bloque de cabecera que simplemente repita solicitudes para expandir ese campo en la tabla din\u00e1mica. Esto puede conducir a un ratio de compresi\u00f3n gigante de 4,096 o mayor, significando que 16kB de datos pueden descomprimirse a 64MB de datos en la m\u00e1quina objetivo."
    }
  ],
  "id": "CVE-2016-6581",
  "lastModified": "2025-04-20T01:37:25.860",
  "metrics": {
    "cvssMetricV2": [
      {
        "acInsufInfo": true,
        "baseSeverity": "HIGH",
        "cvssData": {
          "accessComplexity": "LOW",
          "accessVector": "NETWORK",
          "authentication": "NONE",
          "availabilityImpact": "COMPLETE",
          "baseScore": 7.8,
          "confidentialityImpact": "NONE",
          "integrityImpact": "NONE",
          "vectorString": "AV:N/AC:L/Au:N/C:N/I:N/A:C",
          "version": "2.0"
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        "exploitabilityScore": 10.0,
        "impactScore": 6.9,
        "obtainAllPrivilege": false,
        "obtainOtherPrivilege": false,
        "obtainUserPrivilege": false,
        "source": "nvd@nist.gov",
        "type": "Primary",
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          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
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          "baseScore": 7.5,
          "baseSeverity": "HIGH",
          "confidentialityImpact": "NONE",
          "integrityImpact": "NONE",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
          "version": "3.0"
        },
        "exploitabilityScore": 3.9,
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        "source": "nvd@nist.gov",
        "type": "Primary"
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  "published": "2017-01-10T15:59:00.423",
  "references": [
    {
      "source": "cve@mitre.org",
      "tags": [
        "Third Party Advisory",
        "VDB Entry"
      ],
      "url": "http://www.securityfocus.com/bid/92315"
    },
    {
      "source": "cve@mitre.org",
      "tags": [
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        "Vendor Advisory"
      ],
      "url": "https://python-hyper.org/hpack/en/latest/security/CVE-2016-6581.html"
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      "tags": [
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        "VDB Entry"
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  "vulnStatus": "Deferred",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-399"
        }
      ],
      "source": "nvd@nist.gov",
      "type": "Primary"
    }
  ]
}