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CVE-2021-33766

Estado: AnalizadaAlta (7.5)⚠ Explotación activa💥 Exploit

Microsoft Exchange Server Information Disclosure Vulnerability

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).

CISA KEV — explotada activamente

💥 Exploits públicos

Hay código de explotación o plantillas de detección públicos. No es lo mismo que explotación activa confirmada (KEV), pero aumenta el riesgo: parchee con prioridad.

⚠️ Las pruebas de concepto de GitHub no están verificadas: algunas son falsas o contienen malware. No las ejecute nunca fuera de un laboratorio aislado.

🎯 Técnicas ATT&CK

Cómo se explota esta vulnerabilidad y qué consigue el atacante, en el lenguaje de MITRE ATT&CK.

Vulnerabilidad remota sin autenticación (AV:N/PR:N) en Exchange Server explotable directamente. CVSS alto en confidencialidad indica lectura de datos sensibles del servidor.

Inferido por nuestro agente de análisis a partir de la descripción oficial, el vector CVSS y la CWE, y comprobado por un supervisor. Puede contener errores.

🛡️ Mitigaciones ATT&CK que cubren estas técnicas

Vulnerability ScanningPrivileged Account ManagementNetwork SegmentationLimit Access to Resource Over NetworkFilter Network TrafficApplication Isolation and Sandboxing

Tecnologías afectadas (1)

Microsoft — Exchange Server

CWE

Referencias

JSON original (NVD)

Mostrar
{
  "id": "CVE-2021-33766",
  "cveTags": [],
  "metrics": {
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2021-33766",
          "role": "CISA Coordinator",
          "options": [
            {
              "exploitation": "active"
            },
            {
              "automatable": "yes"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "version": "2.0.3",
          "timestamp": "2025-02-04T19:07:59.976278Z"
        }
      }
    ],
    "cvssMetricV2": [
      {
        "type": "Primary",
        "source": "nvd@nist.gov",
        "cvssData": {
          "version": "2.0",
          "baseScore": 5,
          "accessVector": "NETWORK",
          "vectorString": "AV:N/AC:L/Au:N/C:P/I:N/A:N",
          "authentication": "NONE",
          "integrityImpact": "NONE",
          "accessComplexity": "LOW",
          "availabilityImpact": "NONE",
          "confidentialityImpact": "PARTIAL"
        },
        "acInsufInfo": false,
        "impactScore": 2.9,
        "baseSeverity": "MEDIUM",
        "obtainAllPrivilege": false,
        "exploitabilityScore": 10,
        "obtainUserPrivilege": false,
        "obtainOtherPrivilege": false,
        "userInteractionRequired": false
      }
    ],
    "cvssMetricV31": [
      {
        "type": "Secondary",
        "source": "secure@microsoft.com",
        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.1",
          "baseScore": 7.3,
          "attackVector": "NETWORK",
          "baseSeverity": "HIGH",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L",
          "integrityImpact": "LOW",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "availabilityImpact": "LOW",
          "privilegesRequired": "NONE",
          "confidentialityImpact": "LOW"
        },
        "impactScore": 3.4,
        "exploitabilityScore": 3.9
      },
      {
        "type": "Secondary",
        "source": "nvd@nist.gov",
        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.1",
          "baseScore": 7.5,
          "attackVector": "NETWORK",
          "baseSeverity": "HIGH",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N",
          "integrityImpact": "NONE",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "availabilityImpact": "NONE",
          "privilegesRequired": "NONE",
          "confidentialityImpact": "HIGH"
        },
        "impactScore": 3.6,
        "exploitabilityScore": 3.9
      }
    ]
  },
  "affected": [
    {
      "source": "secure@microsoft.com",
      "affectedData": [
        {
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          "product": "Microsoft Exchange Server 2013 Cumulative Update 23",
          "versions": [
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              "version": "15.00.0",
              "lessThan": "15.00.1497.015",
              "versionType": "custom"
            }
          ],
          "platforms": [
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          ]
        },
        {
          "vendor": "Microsoft",
          "product": "Microsoft Exchange Server 2016 Cumulative Update 19",
          "versions": [
            {
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              "lessThan": "15.01.2176.012",
              "versionType": "custom"
            }
          ],
          "platforms": [
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          ]
        },
        {
          "vendor": "Microsoft",
          "product": "Microsoft Exchange Server 2016 Cumulative Update 20",
          "versions": [
            {
              "status": "affected",
              "version": "15.01.0",
              "lessThan": "15.01.2242.008",
              "versionType": "custom"
            }
          ],
          "platforms": [
            "x64-based Systems"
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        },
        {
          "vendor": "Microsoft",
          "product": "Microsoft Exchange Server 2019 Cumulative Update 8",
          "versions": [
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              "status": "affected",
              "version": "15.02.0",
              "lessThan": "15.02.0792.013",
              "versionType": "custom"
            }
          ],
          "platforms": [
            "x64-based Systems"
          ]
        },
        {
          "vendor": "Microsoft",
          "product": "Microsoft Exchange Server 2019 Cumulative Update 9",
          "versions": [
            {
              "status": "affected",
              "version": "15.02.0",
              "lessThan": "15.02.0858.010",
              "versionType": "custom"
            }
          ],
          "platforms": [
            "x64-based Systems"
          ]
        }
      ]
    }
  ],
  "published": "2021-07-14T18:15:10.380",
  "references": [
    {
      "url": "https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-33766",
      "tags": [
        "Patch",
        "Vendor Advisory"
      ],
      "source": "secure@microsoft.com"
    },
    {
      "url": "https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-33766",
      "tags": [
        "Patch",
        "Vendor Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "https://www.zerodayinitiative.com/advisories/ZDI-21-798/",
      "tags": [
        "Third Party Advisory",
        "VDB Entry"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-33766",
      "tags": [
        "US Government Resource"
      ],
      "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0"
    }
  ],
  "vulnStatus": "Analyzed",
  "weaknesses": [
    {
      "type": "Primary",
      "source": "nvd@nist.gov",
      "description": [
        {
          "lang": "en",
          "value": "NVD-CWE-noinfo"
        }
      ]
    }
  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "Microsoft Exchange Server Information Disclosure Vulnerability"
    },
    {
      "lang": "es",
      "value": "Una vulnerabilidad de Divulgación de Información de Microsoft Exchange"
    }
  ],
  "lastModified": "2026-08-10T19:58:44.540",
  "cisaActionDue": "2022-02-01",
  "cisaExploitAdd": "2022-01-18",
  "configurations": [
    {
      "nodes": [
        {
          "negate": false,
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:a:microsoft:exchange_server:2013:cumulative_update_23:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "DA166F2A-D83B-4D50-AD0B-668D813E0585"
            },
            {
              "criteria": "cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_19:*:*:*:*:*:*",
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            },
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              "matchCriteriaId": "19C1EE0C-B8DD-4B91-BE4B-1C42D72FB718"
            },
            {
              "criteria": "cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_8:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "44ECF39A-1DE1-4870-A494-06A53494338D"
            },
            {
              "criteria": "cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_9:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "71CDF29B-116B-4DE2-AFD0-B62477FF0AEB"
            }
          ],
          "operator": "OR"
        }
      ]
    }
  ],
  "sourceIdentifier": "secure@microsoft.com",
  "cisaRequiredAction": "Apply updates per vendor instructions.",
  "cisaVulnerabilityName": "Microsoft Exchange Server Information Disclosure"
}