CVE-2026-9704

Estado: ModificadaAlta (8.8)—

A flaw was found in Keycloak. An authenticated user with low privileges can exploit this vulnerability by sending an oversized subject_token JSON Web Token (JWT) to the TokenEndpoint. When the token exceeds a 4000-character limit, it is silently dropped, causing the system to fall back to client credentials. This allows the user to gain the permissions of the client's service account, leading to privilege escalation.

CVSS

Versión: 3.1
Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Puntuación base: 8.8

Probabilidad de explotación (EPSS)

Probabilidad de explotación en los próximos 30 días: 0.59%
Percentil entre todas las CVEs puntuadas: 46
Fecha de la puntuación: 4/10/2026

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.

ExplotaciónT1210 Exploitation of Remote Serviceslateral movement85 %
Impacto principalT1068 Exploitation for Privilege Escalationprivilege escalation90 %
Impacto secundarioT1078 Valid Accountsstealth · persistence · privilege escalation · initial access75 %

Vulnerabilidad de servidor Keycloak (AV:N, PR:L) que permite escalada de privilegios mediante token JWT manipulado; atacante autenticado obtiene permisos de cuenta de servicio.

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

Threat Intelligence Program Privileged Account Management Application Isolation and Sandboxing Exploit Protection Update Software Application Developer Guidance

Tecnologías afectadas (1)

Redhat — Build OF Keycloak

CWE

CWE-1284

Referencias

JSON original (NVD)

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