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CVE-2026-65633

Estado: AplazadaAlta (7.6)—

Improper Authentication vulnerability in team-alembic AshAuthentication allows purpose-limited JWTs to be replayed as full bearer API credentials when a resource uses stateless bearer-token verification.

The bearer-token authentication helper AshAuthentication.Plug.Helpers.retrieve_from_bearer/3 verifies an Authorization: Bearer JWT's signature and rejects tokens containing an act claim, but performs no check that the token's purpose claim equals user at the bearer boundary.

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When the resource is configured with require_token_presence_for_authentication?: false (the DSL default), the follow-on validate_token/3 helper returns {:ok, nil} without consulting the token resource, so no downstream check on purpose takes place either. As a result, any valid, non-expired JWT the library itself issued for a narrow, single-purpose flow (most notably the purpose: sign_in token that WebAuthn always emits during sign-in, and that the Password strategy emits when sign-in tokens are enabled) is accepted directly as a general-purpose bearer credential and resolves to a full current_user assignment.

This bypasses the library's intended token-exchange contract, in which the sign_in token is meant to be presented exactly once to a preparation that validates the purpose claim and immediately revokes the token. The first use of a still-valid sign-in token presented directly in the Authorization header succeeds because the stateless bearer path never scopes it to purpose == "user".

An attacker who obtains a not-yet-exchanged sign-in token for a target subject (for example via log or referrer leakage, an intercepted magic-link delivery channel, or a partially compromised intermediary) can present it as a bearer token and be authenticated as that subject, fully bypassing the intended one-time-use and revocation semantics. Exploitation additionally requires that the host application wire up retrieve_from_bearer/3 on a reachable route and uses either WebAuthn (sign-in tokens are always issued) or the Password strategy with sign_in_tokens_enabled?: true. Resources configured with require_token_presence_for_authentication?: true (including applications scaffolded by the Igniter installer since v4.5.0) and the session-based path (authenticate_resource_from_session/4) enforce purpose == "user" against the stored token record and are not affected.

This issue affects ash_authentication: from 3.10.5 before 4.14.2 and from 5.0.0-rc.0 before 5.0.0-rc.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.

Requiere interacción del usuario (UI:P) para obtener el token sign_in. El atacante reutiliza un JWT válido como credencial bearer, asignando identidad de otro usuario sin autenticación legítima, impactando control de acceso (CWE-287).

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

Application Developer GuidanceActive Directory ConfigurationUser TrainingUser Account ManagementPrivileged Account ManagementPassword Policies

Tecnologías afectadas (1)

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

Alembic — ASH AuthenticationAI

CWE

Referencias

JSON original (NVD)

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      "lang": "en",
      "value": "Improper Authentication vulnerability in team-alembic AshAuthentication allows purpose-limited JWTs to be replayed as full bearer API credentials when a resource uses stateless bearer-token verification.\n\nThe bearer-token authentication helper AshAuthentication.Plug.Helpers.retrieve_from_bearer/3 verifies an Authorization: Bearer JWT's signature and rejects tokens containing an act claim, but performs no check that the token's purpose claim equals user at the bearer boundary. When the resource is configured with require_token_presence_for_authentication?: false (the DSL default), the follow-on validate_token/3 helper returns {:ok, nil} without consulting the token resource, so no downstream check on purpose takes place either. As a result, any valid, non-expired JWT the library itself issued for a narrow, single-purpose flow (most notably the purpose: sign_in token that WebAuthn always emits during sign-in, and that the Password strategy emits when sign-in tokens are enabled) is accepted directly as a general-purpose bearer credential and resolves to a full current_user assignment.\n\nThis bypasses the library's intended token-exchange contract, in which the sign_in token is meant to be presented exactly once to a preparation that validates the purpose claim and immediately revokes the token. The first use of a still-valid sign-in token presented directly in the Authorization header succeeds because the stateless bearer path never scopes it to purpose == \"user\".\n\nAn attacker who obtains a not-yet-exchanged sign-in token for a target subject (for example via log or referrer leakage, an intercepted magic-link delivery channel, or a partially compromised intermediary) can present it as a bearer token and be authenticated as that subject, fully bypassing the intended one-time-use and revocation semantics. Exploitation additionally requires that the host application wire up retrieve_from_bearer/3 on a reachable route and uses either WebAuthn (sign-in tokens are always issued) or the Password strategy with sign_in_tokens_enabled?: true. Resources configured with require_token_presence_for_authentication?: true (including applications scaffolded by the Igniter installer since v4.5.0) and the session-based path (authenticate_resource_from_session/4) enforce purpose == \"user\" against the stored token record and are not affected.\n\nThis issue affects ash_authentication: from 3.10.5 before 4.14.2 and from 5.0.0-rc.0 before 5.0.0-rc.13."
    }
  ],
  "lastModified": "2026-09-01T21:15:00.147",
  "sourceIdentifier": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"
}