CVE-2021-3618
Estado: ModificadaAlta (7.4)—
ALPACA is an application layer protocol content confusion attack, exploiting TLS servers implementing different protocols but using compatible certificates, such as multi-domain or wildcard certificates. A MiTM attacker having access to victim's traffic at the TCP/IP layer can redirect traffic from one subdomain to another, resulting in a valid TLS session. This breaks the authentication of TLS and cross-protocol attacks may be possible where the behavior of one protocol service may compromise the other at the application layer.
CVSS
- Versión: 3.1
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
- Puntuación base: 7.4
Probabilidad de explotación (EPSS)
- Probabilidad de explotación en los próximos 30 días: 2.04%
- Percentil entre todas las CVEs puntuadas: 80
- Fecha de la puntuación: 5/10/2026
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)
CWE
- CWE-295
- CWE-295
Referencias
JSON original (NVD)
Mostrar
{
"id": "CVE-2021-3618",
"cveTags": [],
"metrics": {
"cvssMetricV2": [
{
"type": "Primary",
"source": "nvd@nist.gov",
"cvssData": {
"version": "2.0",
"baseScore": 5.8,
"accessVector": "NETWORK",
"vectorString": "AV:N/AC:M/Au:N/C:P/I:P/A:N",
"authentication": "NONE",
"integrityImpact": "PARTIAL",
"accessComplexity": "MEDIUM",
"availabilityImpact": "NONE",
"confidentialityImpact": "PARTIAL"
},
"acInsufInfo": false,
"impactScore": 4.9,
"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": 7.4,
"attackVector": "NETWORK",
"baseSeverity": "HIGH",
"vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N",
"integrityImpact": "HIGH",
"userInteraction": "NONE",
"attackComplexity": "HIGH",
"availabilityImpact": "NONE",
"privilegesRequired": "NONE",
"confidentialityImpact": "HIGH"
},
"impactScore": 5.2,
"exploitabilityScore": 2.2
}
]
},
"affected": [
{
"source": "secalert@redhat.com",
"affectedData": [
{
"vendor": "n/a",
"product": "ALPACA",
"versions": [
{
"status": "affected",
"version": "vsftpd 3.0.4, nginx 1.21.0, sendmail 8.17"
}
]
}
]
}
],
"published": "2022-03-23T20:15:09.833",
"references": [
{
"url": "https://alpaca-attack.com/",
"tags": [
"Third Party Advisory"
],
"source": "secalert@redhat.com"
},
{
"url": "https://bugzilla.redhat.com/show_bug.cgi?id=1975623",
"tags": [
"Issue Tracking",
"Patch",
"Third Party Advisory"
],
"source": "secalert@redhat.com"
},
{
"url": "https://lists.debian.org/debian-lts-announce/2022/11/msg00031.html",
"tags": [
"Mailing List",
"Third Party Advisory"
],
"source": "secalert@redhat.com"
},
{
"url": "https://alpaca-attack.com/",
"tags": [
"Third Party Advisory"
],
"source": "af854a3a-2127-422b-91ae-364da2661108"
},
{
"url": "https://bugzilla.redhat.com/show_bug.cgi?id=1975623",
"tags": [
"Issue Tracking",
"Patch",
"Third Party Advisory"
],
"source": "af854a3a-2127-422b-91ae-364da2661108"
},
{
"url": "https://lists.debian.org/debian-lts-announce/2022/11/msg00031.html",
"tags": [
"Mailing List",
"Third Party Advisory"
],
"source": "af854a3a-2127-422b-91ae-364da2661108"
}
],
"vulnStatus": "Modified",
"weaknesses": [
{
"type": "Secondary",
"source": "secalert@redhat.com",
"description": [
{
"lang": "en",
"value": "CWE-295"
}
]
},
{
"type": "Secondary",
"source": "nvd@nist.gov",
"description": [
{
"lang": "en",
"value": "CWE-295"
}
]
}
],
"descriptions": [
{
"lang": "en",
"value": "ALPACA is an application layer protocol content confusion attack, exploiting TLS servers implementing different protocols but using compatible certificates, such as multi-domain or wildcard certificates. A MiTM attacker having access to victim's traffic at the TCP/IP layer can redirect traffic from one subdomain to another, resulting in a valid TLS session. This breaks the authentication of TLS and cross-protocol attacks may be possible where the behavior of one protocol service may compromise the other at the application layer."
},
{
"lang": "es",
"value": "ALPACA es un ataque de confusión de contenido de protocolo de capa de aplicación, que explota servidores TLS que implementan diferentes protocolos pero que usan certificados compatibles, como certificados multidominio o comodín. Un atacante de tipo MiTM que tenga acceso al tráfico de la víctima en la capa TCP/IP puede redirigir el tráfico de un subdominio a otro, resultando en a una sesión TLS válida. Esto rompe la autenticación de TLS y pueden ser posibles los ataques entre protocolos donde el comportamiento de un servicio de protocolo puede comprometer al otro en la capa de aplicación"
}
],
"lastModified": "2026-06-17T04:05:27.083",
"configurations": [
{
"nodes": [
{
"negate": false,
"cpeMatch": [
{
"criteria": "cpe:2.3:a:f5:nginx:*:*:*:*:*:*:*:*",
"vulnerable": true,
"matchCriteriaId": "777D8DB3-65CF-4A12-BCCE-30849CE07762",
"versionEndExcluding": "1.21.0"
}
],
"operator": "OR"
}
]
},
{
"nodes": [
{
"negate": false,
"cpeMatch": [
{
"criteria": "cpe:2.3:a:sendmail:sendmail:*:*:*:*:*:*:*:*",
"vulnerable": true,
"matchCriteriaId": "2E5DF525-823F-49D0-BDD2-6BCE5EE0F66B",
"versionEndExcluding": "8.17"
}
],
"operator": "OR"
}
]
},
{
"nodes": [
{
"negate": false,
"cpeMatch": [
{
"criteria": "cpe:2.3:a:vsftpd_project:vsftpd:*:*:*:*:*:*:*:*",
"vulnerable": true,
"matchCriteriaId": "CA84E5A7-7557-4805-902B-E8069F5F4091",
"versionEndExcluding": "3.0.4"
}
],
"operator": "OR"
}
]
},
{
"nodes": [
{
"negate": false,
"cpeMatch": [
{
"criteria": "cpe:2.3:o:fedoraproject:fedora:33:*:*:*:*:*:*:*",
"vulnerable": true,
"matchCriteriaId": "E460AA51-FCDA-46B9-AE97-E6676AA5E194"
},
{
"criteria": "cpe:2.3:o:fedoraproject:fedora:34:*:*:*:*:*:*:*",
"vulnerable": true,
"matchCriteriaId": "A930E247-0B43-43CB-98FF-6CE7B8189835"
},
{
"criteria": "cpe:2.3:o:fedoraproject:fedora:35:*:*:*:*:*:*:*",
"vulnerable": true,
"matchCriteriaId": "80E516C0-98A4-4ADE-B69F-66A772E2BAAA"
}
],
"operator": "OR"
}
]
},
{
"nodes": [
{
"negate": false,
"cpeMatch": [
{
"criteria": "cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*",
"vulnerable": true,
"matchCriteriaId": "07B237A9-69A3-4A9C-9DA0-4E06BD37AE73"
}
],
"operator": "OR"
}
]
}
],
"sourceIdentifier": "secalert@redhat.com"
}