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CVE-2026-39849

Estado: AnalizadaAlta (8.7)—

Pi-hole FTL is the core engine of the Pi-hole network-level advertisement and tracker blocker. In versions before 6.6.1, the `dns.interface` configuration field in Pi-hole FTL accepted newline characters without validation, allowing an attacker to inject arbitrary directives into the generated dnsmasq configuration file.

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On installations with no admin password set (the default for many deployments), the configuration API is fully accessible without credentials, allowing a network-adjacent attacker to inject the payload, enable the built-in DHCP server, and achieve arbitrary command execution on the host the next time any device on the network requests a DHCP lease. The injected value is persisted to /etc/pihole/pihole.toml and survives restarts. The strncpy in the code path limits the total interface field to 31 bytes, but payloads such as wlan0\ndhcp-script=/tmp/p fit within this constraint. The dnsmasq config validation introduced in FTL 6.6 only checks syntactic validity, so valid directives injected via newline pass validation successfully. This issue has been fixed in version 6.6.1.

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.

Acceso de red con privilegios mínimos (PR:L) a API sin autenticación en configuración por defecto. Inyección de directivas en dnsmasq permite ejecución de comandos arbitrarios al solicitar DHCP, modificación de configuración persistente.

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 ManagementDisable or Remove Feature or ProgramRestrict File and Directory PermissionsNetwork SegmentationVulnerability ScanningUser Account Management

Tecnologías afectadas (1)

Pi-hole — Ftldns

CWE

Referencias

JSON original (NVD)

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  "id": "CVE-2026-39849",
  "cveTags": [],
  "metrics": {
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        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
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          "role": "CISA Coordinator",
          "options": [
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              "exploitation": "poc"
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            {
              "automatable": "no"
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            {
              "technicalImpact": "total"
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          "version": "2.0.3",
          "timestamp": "2026-05-08T03:55:36.195107Z"
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          "vulnerabilityResponseEffort": "NOT_DEFINED",
          "modifiedSubAvailabilityImpact": "NOT_DEFINED",
          "modifiedVulnAvailabilityImpact": "NOT_DEFINED",
          "modifiedSubConfidentialityImpact": "NOT_DEFINED",
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      "lang": "en",
      "value": "Pi-hole FTL is the core engine of the Pi-hole network-level advertisement and tracker blocker. In versions before 6.6.1, the `dns.interface` configuration field in Pi-hole FTL accepted newline characters without validation, allowing an attacker to inject arbitrary directives into the generated dnsmasq configuration file. On installations with no admin password set (the default for many deployments), the configuration API is fully accessible without credentials, allowing a network-adjacent attacker to inject the payload, enable the built-in DHCP server, and achieve arbitrary command execution on the host the next time any device on the network requests a DHCP lease. The injected value is persisted to /etc/pihole/pihole.toml and survives restarts. The strncpy in the code path limits the total interface field to 31 bytes, but payloads such as wlan0\\ndhcp-script=/tmp/p fit within this constraint. The dnsmasq config validation introduced in FTL 6.6 only checks syntactic validity, so valid directives injected via newline pass validation successfully. This issue has been fixed in version 6.6.1."
    },
    {
      "lang": "es",
      "value": "Pi-hole FTL es el motor central del bloqueador de anuncios y rastreadores a nivel de red de Pi-hole. En versiones anteriores a la 6.6.1, el campo de configuración 'dns.interface' en Pi-hole FTL aceptaba caracteres de nueva línea sin validación, permitiendo a un atacante inyectar directivas arbitrarias en el archivo de configuración de dnsmasq generado. En instalaciones sin contraseña de administrador configurada (el valor predeterminado para muchas implementaciones), la API de configuración es totalmente accesible sin credenciales, permitiendo a un atacante adyacente a la red inyectar la carga útil, habilitar el servidor DHCP integrado y lograr la ejecución arbitraria de comandos en el host la próxima vez que cualquier dispositivo en la red solicite una concesión DHCP. El valor inyectado se persiste en /etc/pihole/pihole.toml y sobrevive a los reinicios. La función strncpy en la ruta del código limita el campo de interfaz total a 31 bytes, pero cargas útiles como wlan0\\ndhcp-script=/tmp/p encajan dentro de esta restricción. La validación de configuración de dnsmasq introducida en FTL 6.6 solo verifica la validez sintáctica, por lo que las directivas válidas inyectadas a través de una nueva línea pasan la validación con éxito. Este problema ha sido solucionado en la versión 6.6.1."
    }
  ],
  "lastModified": "2026-07-24T21:10:00.143",
  "configurations": [
    {
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