CVE-2026-40478

Estado: ModificadaCrítica (9)—

Thymeleaf is a server-side Java template engine for web and standalone environments. Versions 3.1.3.RELEASE and prior contain a security bypass vulnerability in the the expression execution mechanisms. Although the library provides mechanisms to prevent expression injection, it fails to properly neutralize specific syntax patterns that allow for the execution of unauthorized expressions. If an application developer passes unvalidated user input directly to the template engine, an unauthenticated remote attacker can bypass the library's protections to achieve Server-Side Template Injection (SSTI). This issue has ben fixed in version 3.1.4.RELEASE.

CVSS

Versión: 3.1
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H
Puntuación base: 9

Probabilidad de explotación (EPSS)

Probabilidad de explotación en los próximos 30 días: 1.20%
Percentil entre todas las CVEs puntuadas: 67
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.

ExplotaciónT1190 Exploit Public-Facing Applicationinitial access95 %
Impacto principalT1059 Command and Scripting Interpreterexecution90 %
Impacto secundarioT1565 Data Manipulationimpact70 %

AV:N sin autenticación (PR:N) indica aplicación expuesta. SSTI permite ejecutar código en el servidor Java. CWE-917 (expresiones no neutralizadas) sustenta ejecución de comandos.

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 Network Segmentation Vulnerability Scanning Restrict Web-Based Content Restrict File and Directory Permissions Remote Data Storage

Tecnologías afectadas (1)

Thymeleaf — Thymeleaf

CWE

CWE-917, CWE-1336
CWE-917

Referencias

JSON original (NVD)

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      "value": "Thymeleaf is a server-side Java template engine for web and standalone environments. Versions 3.1.3.RELEASE and prior contain a security bypass vulnerability in the the expression execution mechanisms. Although the library provides mechanisms to prevent expression injection, it fails to properly neutralize specific syntax patterns that allow for the execution of unauthorized expressions. If an application developer passes unvalidated user input directly to the template engine, an unauthenticated remote attacker can bypass the library's protections to achieve Server-Side Template Injection (SSTI). This issue has ben fixed in version 3.1.4.RELEASE."
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