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CVE-2021-32749

Estado: ModificadaAlta (8.1)—

fail2ban es un demonio para banear hosts que causan múltiples errores de autenticación. En versiones 0.9.7 y anteriores, versiones 0.10.0 hasta 0.10.6, y versiones 0.11.0 hasta 0.11.2, se presenta una vulnerabilidad que conlleva a una posible ejecución de código remota en la acción de correo mail-whois. El comando "mail" del paquete mailutils usado en acciones de correo como "mail-whois" puede ejecutar comando si se presentan secuencias sin mayúsculas ("\n~") en la entrada "foreign" (por ejemplo, en la salida de whois).

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Para explotar la vulnerabilidad, un atacante necesitaría insertar caracteres maliciosos en la respuesta enviada por el servidor whois, ya sea por medio de un ataque MITM o al tomar el control de un servidor whois. El problema está parcheado en las versiones 0.10.7 y 0.11.3. Como solución, se puede evitar el uso de la acción "mail-whois" o parchear la vulnerabilidad manualmente

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 (2)

Fail2ban — Fail2banFedoraproject — Fedora

CWE

Referencias

JSON original (NVD)

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{
  "id": "CVE-2021-32749",
  "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": "Secondary",
        "source": "security-advisories@github.com",
        "cvssData": {
          "scope": "CHANGED",
          "version": "3.1",
          "baseScore": 6.1,
          "attackVector": "NETWORK",
          "baseSeverity": "MEDIUM",
          "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:N/I:H/A:N",
          "integrityImpact": "HIGH",
          "userInteraction": "REQUIRED",
          "attackComplexity": "HIGH",
          "availabilityImpact": "NONE",
          "privilegesRequired": "NONE",
          "confidentialityImpact": "NONE"
        },
        "impactScore": 4,
        "exploitabilityScore": 1.6
      },
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          "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"
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        "impactScore": 5.9,
        "exploitabilityScore": 2.2
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          "product": "fail2ban",
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  "published": "2021-07-16T18:15:08.270",
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      "source": "security-advisories@github.com"
    },
    {
      "url": "https://security.gentoo.org/glsa/202310-13",
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      "source": "af854a3a-2127-422b-91ae-364da2661108"
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      "source": "af854a3a-2127-422b-91ae-364da2661108"
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  ],
  "vulnStatus": "Modified",
  "weaknesses": [
    {
      "type": "Secondary",
      "source": "security-advisories@github.com",
      "description": [
        {
          "lang": "en",
          "value": "CWE-78"
        }
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    },
    {
      "type": "Primary",
      "source": "nvd@nist.gov",
      "description": [
        {
          "lang": "en",
          "value": "CWE-94"
        }
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  ],
  "descriptions": [
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      "lang": "en",
      "value": "fail2ban is a daemon to ban hosts that cause multiple authentication errors. In versions 0.9.7 and prior, 0.10.0 through 0.10.6, and 0.11.0 through 0.11.2, there is a vulnerability that leads to possible remote code execution in the mailing action mail-whois. Command `mail` from mailutils package used in mail actions like `mail-whois` can execute command if unescaped sequences (`\\n~`) are available in \"foreign\" input (for instance in whois output). To exploit the vulnerability, an attacker would need to insert malicious characters into the response sent by the whois server, either via a MITM attack or by taking over a whois server. The issue is patched in versions 0.10.7 and 0.11.3. As a workaround, one may avoid the usage of action `mail-whois` or patch the vulnerability manually."
    },
    {
      "lang": "es",
      "value": "fail2ban es un demonio para banear hosts que causan múltiples errores de autenticación. En versiones 0.9.7 y anteriores, versiones 0.10.0 hasta 0.10.6, y versiones 0.11.0 hasta 0.11.2, se presenta una vulnerabilidad que conlleva a una posible ejecución de código remota en la acción de correo mail-whois. El comando \"mail\" del paquete mailutils usado en acciones de correo como \"mail-whois\" puede ejecutar comando si se presentan secuencias sin mayúsculas (\"\\n~\") en la entrada \"foreign\" (por ejemplo, en la salida de whois). Para explotar la vulnerabilidad, un atacante necesitaría insertar caracteres maliciosos en la respuesta enviada por el servidor whois, ya sea por medio de un ataque MITM o al tomar el control de un servidor whois. El problema está parcheado en las versiones 0.10.7 y 0.11.3. Como solución, se puede evitar el uso de la acción \"mail-whois\" o parchear la vulnerabilidad manualmente"
    }
  ],
  "lastModified": "2026-06-17T03:53:33.277",
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