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CVE-2026-40934

Estado: AnalizadaAlta (7.6)—

Jupyter Server is the backend for Jupyter web applications. In versions 2.17.0 and earlier, the secret used to sign authentication cookies is persisted to a static file at ~/.local/share/jupyter/runtime/jupyter_cookie_secret and is never rotated when a user changes their password. After a password reset and server restart, any previously issued authentication cookie remains cryptographically valid because the signing key has not changed. An attacker who has captured a session cookie through any means retains full authenticated access to the server regardless of subsequent password changes.

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This affects deployments using password-based authentication, particularly shared or public-facing servers where credential rotation is expected to revoke existing sessions. This issue has been fixed in version 2.18.0.

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.

Acceso remoto autenticado (PR:L, AV:N) explotando cookie firmada estática no rotada tras cambio de contraseña. Permite mantener sesión válida (T1078.001) y expone secreto en almacenamiento local (T1552.001).

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

Password PoliciesVulnerability ScanningUser TrainingThreat Intelligence ProgramRestrict File and Directory PermissionsPrivileged Account Management

Tecnologías afectadas (1)

Jupyter — Jupyter Server

CWE

Referencias

JSON original (NVD)

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  "id": "CVE-2026-40934",
  "cveTags": [],
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          "options": [
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              "technicalImpact": "total"
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          "value": "CWE-613"
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      "lang": "en",
      "value": "Jupyter Server is the backend for Jupyter web applications. In versions 2.17.0 and earlier, the secret used to sign authentication cookies is persisted to a static file at ~/.local/share/jupyter/runtime/jupyter_cookie_secret and is never rotated when a user changes their password. After a password reset and server restart, any previously issued authentication cookie remains cryptographically valid because the signing key has not changed. An attacker who has captured a session cookie through any means retains full authenticated access to the server regardless of subsequent password changes. This affects deployments using password-based authentication, particularly shared or public-facing servers where credential rotation is expected to revoke existing sessions. This issue has been fixed in version 2.18.0."
    },
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      "lang": "es",
      "value": "Jupyter Server es el backend para las aplicaciones web de Jupyter. En las versiones 2.17.0 y anteriores, el secreto utilizado para firmar las cookies de autenticación se persiste en un archivo estático en ~/.local/share/jupyter/runtime/jupyter_cookie_secret y nunca se rota cuando un usuario cambia su contraseña. Después de un restablecimiento de contraseña y un reinicio del servidor, cualquier cookie de autenticación emitida previamente permanece criptográficamente válida porque la clave de firma no ha cambiado. Un atacante que ha capturado una cookie de sesión por cualquier medio retiene acceso autenticado completo al servidor independientemente de los cambios de contraseña posteriores. Esto afecta a las implementaciones que utilizan autenticación basada en contraseña, particularmente servidores compartidos o de cara al público donde se espera que la rotación de credenciales revoque las sesiones existentes. Este problema ha sido solucionado en la versión 2.18.0."
    }
  ],
  "lastModified": "2026-07-25T11:10:00.100",
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