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CVE-2021-20235

Estado: ModificadaAlta (8.1)—

There's a flaw in the zeromq server in versions before 4.3.3 in src/decoder_allocators.hpp. The decoder static allocator could have its sized changed, but the buffer would remain the same as it is a static buffer. A remote, unauthenticated attacker who sends a crafted request to the zeromq server could trigger a buffer overflow WRITE of arbitrary data if CURVE/ZAP authentication is not enabled. The greatest impact of this flaw is to application availability, data integrity, and confidentiality.

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 (1)

Zeromq — Libzmq

CWE

Referencias

JSON original (NVD)

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{
  "id": "CVE-2021-20235",
  "cveTags": [],
  "metrics": {
    "cvssMetricV2": [
      {
        "type": "Primary",
        "source": "nvd@nist.gov",
        "cvssData": {
          "version": "2.0",
          "baseScore": 6.8,
          "accessVector": "NETWORK",
          "vectorString": "AV:N/AC:M/Au:N/C:P/I:P/A:P",
          "authentication": "NONE",
          "integrityImpact": "PARTIAL",
          "accessComplexity": "MEDIUM",
          "availabilityImpact": "PARTIAL",
          "confidentialityImpact": "PARTIAL"
        },
        "acInsufInfo": false,
        "impactScore": 6.4,
        "baseSeverity": "MEDIUM",
        "obtainAllPrivilege": false,
        "exploitabilityScore": 8.6,
        "obtainUserPrivilege": false,
        "obtainOtherPrivilege": false,
        "userInteractionRequired": false
      }
    ],
    "cvssMetricV31": [
      {
        "type": "Primary",
        "source": "nvd@nist.gov",
        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.1",
          "baseScore": 8.1,
          "attackVector": "NETWORK",
          "baseSeverity": "HIGH",
          "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H",
          "integrityImpact": "HIGH",
          "userInteraction": "NONE",
          "attackComplexity": "HIGH",
          "availabilityImpact": "HIGH",
          "privilegesRequired": "NONE",
          "confidentialityImpact": "HIGH"
        },
        "impactScore": 5.9,
        "exploitabilityScore": 2.2
      }
    ]
  },
  "affected": [
    {
      "source": "secalert@redhat.com",
      "affectedData": [
        {
          "vendor": "n/a",
          "product": "zeromq",
          "versions": [
            {
              "status": "affected",
              "version": "zeromq 4.3.3"
            }
          ]
        }
      ]
    }
  ],
  "published": "2021-04-01T14:15:13.217",
  "references": [
    {
      "url": "https://bugzilla.redhat.com/show_bug.cgi?id=1921983",
      "tags": [
        "Issue Tracking",
        "Patch",
        "Third Party Advisory"
      ],
      "source": "secalert@redhat.com"
    },
    {
      "url": "https://github.com/zeromq/libzmq/security/advisories/GHSA-fc3w-qxf5-7hp6",
      "tags": [
        "Patch",
        "Third Party Advisory"
      ],
      "source": "secalert@redhat.com"
    },
    {
      "url": "https://bugzilla.redhat.com/show_bug.cgi?id=1921983",
      "tags": [
        "Issue Tracking",
        "Patch",
        "Third Party Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "https://github.com/zeromq/libzmq/security/advisories/GHSA-fc3w-qxf5-7hp6",
      "tags": [
        "Patch",
        "Third Party Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    }
  ],
  "vulnStatus": "Modified",
  "weaknesses": [
    {
      "type": "Secondary",
      "source": "secalert@redhat.com",
      "description": [
        {
          "lang": "en",
          "value": "CWE-120"
        }
      ]
    },
    {
      "type": "Primary",
      "source": "nvd@nist.gov",
      "description": [
        {
          "lang": "en",
          "value": "CWE-787"
        }
      ]
    }
  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "There's a flaw in the zeromq server in versions before 4.3.3 in src/decoder_allocators.hpp. The decoder static allocator could have its sized changed, but the buffer would remain the same as it is a static buffer. A remote, unauthenticated attacker who sends a crafted request to the zeromq server could trigger a buffer overflow WRITE of arbitrary data if CURVE/ZAP authentication is not enabled. The greatest impact of this flaw is to application availability, data integrity, and confidentiality."
    },
    {
      "lang": "es",
      "value": "Se presenta un fallo en el servidor zeromq en versiones anteriores a 4.3.3, en el archivo src/decoder_allocators.hpp. Se podría cambiar el tamaño del asignador estático del decodificador, pero el búfer permanecería igual, ya que es un búfer estático. Un atacante no autenticado remoto que envía una petición diseñada al servidor zeromq podría desencadenar un desbordamiento del búfer WRITE de datos arbitrarios si la autenticación CURVE/ZAP no está habilitada. El mayor impacto de este fallo es la disponibilidad de la aplicación, la integridad de los datos y la confidencialidad."
    }
  ],
  "lastModified": "2026-06-17T03:33:31.373",
  "configurations": [
    {
      "nodes": [
        {
          "negate": false,
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:a:zeromq:libzmq:*:*:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "C1384189-AC6C-4847-A3BF-FB7A3A826F75",
              "versionEndExcluding": "4.3.3",
              "versionStartIncluding": "4.2.0"
            }
          ],
          "operator": "OR"
        }
      ]
    }
  ],
  "sourceIdentifier": "secalert@redhat.com"
}