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CVE-2026-27586

Estado: AnalizadaAlta (8.8)—

Caddy is an extensible server platform that uses TLS by default. Prior to version 2.11.1, two swallowed errors in `ClientAuthentication.provision()` cause mTLS client certificate authentication to silently fail open when a CA certificate file is missing, unreadable, or malformed. The server starts without error but accepts any client certificate signed by any system-trusted CA, completely bypassing the intended private CA trust boundary.

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Any deployment using `trusted_ca_cert_file` or `trusted_ca_certs_pem_files` for mTLS will silently degrade to accepting any system-trusted client certificate if the CA file becomes unavailable. This can happen due to a typo in the path, file rotation, corruption, or permission changes. The server gives no indication that mTLS is misconfigured. Version 2.11.1 fixes the 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).

🎯 Técnicas ATT&CK

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

Caddy expone servicio de autenticación mTLS en red sin privilegios previos (AV:N, PR:N); el error silencioso permite autenticación con CAs del sistema, otorgando acceso no autorizado (T1078.001) y comprometiendo el control de acceso de cuenta (T1556.004).

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 ManagementMulti-factor AuthenticationVulnerability ScanningPassword PoliciesNetwork SegmentationLimit Access to Resource Over Network

Tecnologías afectadas (1)

Caddyserver — Caddy

CWE

Referencias

JSON original (NVD)

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      "value": "Caddy is an extensible server platform that uses TLS by default. Prior to version 2.11.1, two swallowed errors in `ClientAuthentication.provision()` cause mTLS client certificate authentication to silently fail open when a CA certificate file is missing, unreadable, or malformed. The server starts without error but accepts any client certificate signed by any system-trusted CA, completely bypassing the intended private CA trust boundary. Any deployment using `trusted_ca_cert_file` or `trusted_ca_certs_pem_files` for mTLS will silently degrade to accepting any system-trusted client certificate if the CA file becomes unavailable. This can happen due to a typo in the path, file rotation, corruption, or permission changes. The server gives no indication that mTLS is misconfigured. Version 2.11.1 fixes the vulnerability."
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      "value": "Caddy es una plataforma de servidor extensible que usa TLS por defecto. Antes de la versión 2.11.1, dos errores silenciados en `ClientAuthentication.provision()` causan que la autenticación de certificados de cliente mTLS falle silenciosamente en modo abierto cuando un archivo de certificado de CA falta, es ilegible o está malformado. El servidor se inicia sin error pero acepta cualquier certificado de cliente firmado por cualquier CA de confianza del sistema, eludiendo completamente el límite de confianza de CA privada previsto. Cualquier despliegue que use `trusted_ca_cert_file` o `trusted_ca_certs_pem_files` para mTLS se degradará silenciosamente para aceptar cualquier certificado de cliente de confianza del sistema si el archivo de CA deja de estar disponible. Esto puede ocurrir debido a un error tipográfico en la ruta, rotación de archivos, corrupción o cambios de permisos. El servidor no da ninguna indicación de que mTLS está mal configurado. La versión 2.11.1 corrige la vulnerabilidad."
    }
  ],
  "lastModified": "2026-06-17T10:27:20.880",
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