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CVE-2026-26308

Estado: AnalizadaAlta (8.2)—

Envoy is a high-performance edge/middle/service proxy. Prior to 1.37.1, 1.36.5, 1.35.8, and 1.34.13, the Envoy RBAC (Role-Based Access Control) filter contains a logic vulnerability in how it validates HTTP headers when multiple values are present for the same header name. Instead of validating each header value individually, Envoy concatenates all values into a single comma-separated string. This behavior allows attackers to bypass RBAC policies—specifically "Deny" rules—by sending duplicate headers, effectively obscuring the malicious value from exact-match mechanisms. This vulnerability is fixed in 1.37.1, 1.36.5, 1.35.8, and 1.34.13.

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).

🎯 Técnicas ATT&CK

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

Vulnerabilidad en RBAC remoto (AV:N, PR:N, UI:N) que bypasea políticas Deny mediante headers duplicados, permitiendo acceso no autorizado. Impacto confidencialidad alta (C:H).

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

Privileged Account ManagementApplication Developer GuidanceActive Directory ConfigurationVulnerability ScanningUser TrainingUser Account Management

Tecnologías afectadas (1)

Envoyproxy — Envoy

CWE

Referencias

JSON original (NVD)

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      "value": "Envoy is a high-performance edge/middle/service proxy. Prior to 1.37.1, 1.36.5, 1.35.8, and 1.34.13, the Envoy RBAC (Role-Based Access Control) filter contains a logic vulnerability in how it validates HTTP headers when multiple values are present for the same header name. Instead of validating each header value individually, Envoy concatenates all values into a single comma-separated string. This behavior allows attackers to bypass RBAC policies—specifically \"Deny\" rules—by sending duplicate headers, effectively obscuring the malicious value from exact-match mechanisms. This vulnerability is fixed in 1.37.1, 1.36.5, 1.35.8, and 1.34.13."
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      "value": "Envoy es un proxy de alto rendimiento de borde/intermedio/servicio. Antes de 1.37.1, 1.36.5, 1.35.8 y 1.34.13, el filtro RBAC (control de acceso basado en roles) de Envoy contiene una vulnerabilidad lógica en cómo valida los encabezados HTTP cuando hay múltiples valores presentes para el mismo nombre de encabezado. En lugar de validar cada valor de encabezado individualmente, Envoy concatena todos los valores en una única cadena separada por comas. Este comportamiento permite a los atacantes eludir las políticas RBAC —específicamente las reglas de 'Denegar'— enviando encabezados duplicados, ocultando eficazmente el valor malicioso de los mecanismos de coincidencia exacta. Esta vulnerabilidad está corregida en 1.37.1, 1.36.5, 1.35.8 y 1.34.13."
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