CVE-2026-20051
Estado: AplazadaAlta (7.4)—
A vulnerability with the Ethernet VPN (EVPN) Layer 2 ingress packet processing of Cisco Nexus 3600 Platform Switches and Cisco Nexus 9500-R Series Switching Platforms could allow an unauthenticated, adjacent attacker to trigger a Layer 2 traffic loop.
Detalles técnicos trazas, registros y código del informe original
This vulnerability is due to a logic error when processing a crafted Layer 2 ingress frame. An attacker could exploit this vulnerability by sending a stream of crafted Ethernet frames through the targeted device. A successful exploit could allow the attacker to cause a Layer 2 Virtual eXtensible LAN (VxLAN) traffic loop, which, in turn, could result in a denial of service (DoS) condition. This Layer 2 loop could oversubscribe the bandwidth on network interfaces, which would result in all data plane traffic being dropped. To exploit this vulnerability, the attacker must be Layer 2-adjacent to the affected device. Note: To stop active exploitation of this vulnerability, manual intervention is required to both stop the crafted traffic and flap all involved network interfaces. For additional assistance if a Layer 2 loop that is related to this vulnerability is suspected, contact the Cisco Technical Assistance Center (TAC) or the proper support provider.
CVSS
- Versión: 3.1
- Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
- Puntuación base: 7.4
Probabilidad de explotación (EPSS)
- Probabilidad de explotación en los próximos 30 días: 0.16%
- Percentil entre todas las CVEs puntuadas: 5
- Fecha de la puntuación: 6/10/2026
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).
🎯 Técnicas ATT&CK
Cómo se explota esta vulnerabilidad y qué consigue el atacante, en el lenguaje de MITRE ATT&CK.
- Explotación
T1210Exploitation of Remote Serviceslateral movement95 % - Impacto principal
T1499.004Application or System Exploitationimpact90 %
Vector AV:A (adyacente) + acceso remoto a servicio de red (EVPN/L2) sin autenticación ni privilegios = T1210. Impacto: DoS por saturación de ancho de banda en bucle de tráfico L2, encaja en T1499.004 (Network Bandwidth Exhaustion).
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
Tecnologías afectadas (2)
⚠ Inferidas por IA a partir de la descripción — NVD aún no ha analizado esta CVE; no son CPE verificados.
CWE
- CWE-457
Referencias
JSON original (NVD)
Mostrar
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"value": "A vulnerability with the Ethernet VPN (EVPN) Layer 2 ingress packet processing of Cisco Nexus 3600 Platform Switches and Cisco Nexus 9500-R Series Switching Platforms could allow an unauthenticated, adjacent attacker to trigger a Layer 2 traffic loop.\r\n\r\nThis vulnerability is due to a logic error when processing a crafted Layer 2 ingress frame. An attacker could exploit this vulnerability by sending a stream of crafted Ethernet frames through the targeted device. A successful exploit could allow the attacker to cause a Layer 2 Virtual eXtensible LAN (VxLAN) traffic loop, which, in turn, could result in a denial of service (DoS) condition. This Layer 2 loop could oversubscribe the bandwidth on network interfaces, which would result in all data plane traffic being dropped. To exploit this vulnerability, the attacker must be Layer 2-adjacent to the affected device.\r\nNote: To stop active exploitation of this vulnerability, manual intervention is required to both stop the crafted traffic and flap all involved network interfaces. For additional assistance if a Layer 2 loop that is related to this vulnerability is suspected, contact the Cisco Technical Assistance Center (TAC) or the proper support provider. "
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"value": "Una vulnerabilidad en el procesamiento de paquetes de entrada de Capa 2 de Ethernet VPN (EVPN) de los switches de plataforma Cisco Nexus 3600 y las plataformas de switching Cisco Nexus 9500-R Series podría permitir a un atacante adyacente no autenticado desencadenar un bucle de tráfico de Capa 2.\n\nEsta vulnerabilidad se debe a un error de lógica al procesar una trama de entrada de Capa 2 manipulada. Un atacante podría explotar esta vulnerabilidad enviando un flujo de tramas Ethernet manipuladas a través del dispositivo objetivo. Un exploit exitoso podría permitir al atacante causar un bucle de tráfico de Capa 2 de Virtual eXtensible LAN (VxLAN), lo que, a su vez, podría resultar en una condición de denegación de servicio (DoS). Este bucle de Capa 2 podría sobresaturar el ancho de banda en las interfaces de red, lo que resultaría en la caída de todo el tráfico del plano de datos. Para explotar esta vulnerabilidad, el atacante debe ser adyacente en Capa 2 al dispositivo afectado.\nNota: Para detener la explotación activa de esta vulnerabilidad, se requiere intervención manual tanto para detener el tráfico manipulado como para reiniciar todas las interfaces de red involucradas. Para asistencia adicional si se sospecha de un bucle de Capa 2 relacionado con esta vulnerabilidad, contacte con el Centro de Asistencia Técnica de Cisco (TAC) o con el proveedor de soporte adecuado."
}
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"lastModified": "2026-06-17T10:16:58.923",
"sourceIdentifier": "psirt@cisco.com"
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