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CVE-2026-39418

Estado: AnalizadaAlta (7.4)—

MaxKB is an open-source AI assistant for enterprise. In versions 2.7.1 and below, sandbox network protection can be bypassed by using socket.sendto() with the MSG_FASTOPEN flag. This allows authenticated user with tool-editing permissions to reach internal services that are explicitly blocked by the sandbox's banned hosts configuration.

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MaxKB's sandbox uses LD_PRELOAD to hook the connect() function and block connections to banned IPs, but Linux's sendto() with the MSG_FASTOPEN flag can establish TCP connections directly through the kernel without ever calling connect(), completely bypassing the IP validation. Although sendto is listed in the syscall() wrapper, this is ineffective because glibc invokes the kernel syscall directly rather than routing through the hooked syscall() function. This issue has been fixed in version 2.8.0.

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 de bypass de sandbox en MaxKB que permite a usuario autenticado (PR:L) alcanzar servicios internos bloqueados (CWE-918: SSRF). El bypass del LD_PRELOAD mediante sendto() con MSG_FASTOPEN (acceso a red interna) y potencial lectura de datos de servicios internos.

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

Vulnerability ScanningThreat Intelligence ProgramSSL/TLS InspectionPrivileged Account ManagementNetwork SegmentationNetwork Intrusion Prevention

Tecnologías afectadas (1)

Maxkb — Maxkb

CWE

Referencias

JSON original (NVD)

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{
  "id": "CVE-2026-39418",
  "cveTags": [],
  "metrics": {
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-39418",
          "role": "CISA Coordinator",
          "options": [
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              "exploitation": "none"
            },
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              "automatable": "no"
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          "version": "2.0.3",
          "timestamp": "2026-04-14T15:54:18.732139Z"
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  "published": "2026-04-14T01:16:04.353",
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      "value": "MaxKB is an open-source AI assistant for enterprise. In versions 2.7.1 and below, sandbox network protection can be bypassed by using socket.sendto() with the MSG_FASTOPEN flag. This allows authenticated user with tool-editing permissions to reach internal services that are explicitly blocked by the sandbox's banned hosts configuration. MaxKB's sandbox uses LD_PRELOAD to hook the connect() function and block connections to banned IPs, but Linux's sendto() with the MSG_FASTOPEN flag can establish TCP connections directly through the kernel without ever calling connect(), completely bypassing the IP validation. Although sendto is listed in the syscall() wrapper, this is ineffective because glibc invokes the kernel syscall directly rather than routing through the hooked syscall() function. This issue has been fixed in version 2.8.0."
    }
  ],
  "lastModified": "2026-06-17T10:42:05.177",
  "configurations": [
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