CVE-2026-53425

Estado: Pendiente de análisisAlta (7.6)—

Insufficient Verification of Data Authenticity vulnerability in dropbox samly allows an attacker to establish an authenticated session using a SAML response the service provider never requested.

Samly.SPHandler.validate_authresp/3 in lib/samly/sp_handler.ex validates a SAML response for the SP-initiated flow by comparing only the RelayState value, the IdP identifier, and the presence of a target URL held in the session.

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It never compares SubjectConfirmationData/@InResponseTo against the ID of the AuthnRequest the service provider issued, and that request ID is never persisted, so no comparison is possible. SAML 2.0 Core section 4.1.4.3 requires a service provider to reject a response whose InResponseTo does not match a request it made. The underlying esaml library checks status, signature, recipient, audience, and staleness, but likewise never inspects InResponseTo, so nothing else closes the gap. Exploitation requires a validly signed assertion from the trusted IdP, which an attacker can obtain for their own account, and a RelayState matching the victim's session; the assertion signature itself remains intact, so this is not a signature-forgery issue.

This issue affects samly: from 0.3.0 onward.

CVSS

Versión: 4.0
Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Puntuación base: 7.6

Probabilidad de explotación (EPSS)

Probabilidad de explotación en los próximos 30 días: 0.22%
Percentil entre todas las CVEs puntuadas: 12
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.

ExplotaciónT1203 Exploitation for Client Executionexecution85 %
Impacto principalT1078.004 Cloud Accountsstealth · persistence · privilege escalation · initial access90 %
Impacto secundarioT1556.003 Pluggable Authentication Modulesdefense impairment · persistence · credential access75 %

Vector CVSS con UI:P (interacción del usuario) indica ejecución en cliente. El atacante reutiliza una aserción SAML válida firmada por IdP confiado para establecer sesión autenticada sin validar InResponseTo, permitiendo secuestro de sesión mediante respuesta SAML no solicitada.

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 Management Multi-factor Authentication Active Directory Configuration User Training User Account Management Password Policies

Tecnologías afectadas (1)

⚠ Inferidas por IA a partir de la descripción — NVD aún no ha analizado esta CVE; no son CPE verificados.

Dropbox — Samly^AI

CWE

CWE-345

Referencias

JSON original (NVD)

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  "id": "CVE-2026-53425",
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          "options": [
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              "automatable": "no"
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            {
              "technicalImpact": "total"
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          "timestamp": "2026-08-21T19:50:24.245049Z"
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  "published": "2026-08-20T18:16:27.850",
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      "url": "https://cna.erlef.org/cves/CVE-2026-53425.html",
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"
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    {
      "lang": "en",
      "value": "Insufficient Verification of Data Authenticity vulnerability in dropbox samly allows an attacker to establish an authenticated session using a SAML response the service provider never requested.\n\nSamly.SPHandler.validate_authresp/3 in lib/samly/sp_handler.ex validates a SAML response for the SP-initiated flow by comparing only the RelayState value, the IdP identifier, and the presence of a target URL held in the session. It never compares SubjectConfirmationData/@InResponseTo against the ID of the AuthnRequest the service provider issued, and that request ID is never persisted, so no comparison is possible. SAML 2.0 Core section 4.1.4.3 requires a service provider to reject a response whose InResponseTo does not match a request it made. The underlying esaml library checks status, signature, recipient, audience, and staleness, but likewise never inspects InResponseTo, so nothing else closes the gap. Exploitation requires a validly signed assertion from the trusted IdP, which an attacker can obtain for their own account, and a RelayState matching the victim's session; the assertion signature itself remains intact, so this is not a signature-forgery issue.\n\nThis issue affects samly: from 0.3.0 onward."
    }
  ],
  "lastModified": "2026-08-24T16:47:56.007",
  "sourceIdentifier": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"
}