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.

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 expression execution mechanisms. Although the library provides mechanisms to prevent expression injection, it fails to properly restrict the scope of accessible objects, allowing specific potentially sensitive objects to be reached from within a template. 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.

Thymeleaf through 3.1.1.RELEASE, as used in spring-boot-admin (aka Spring Boot Admin) through 3.1.1 and other products, allows sandbox bypass via crafted HTML. This may be relevant for SSTI (Server Side Template Injection) and code execution in spring-boot-admin if MailNotifier is enabled and there is write access to environment variables via the UI.

In the thymeleaf-spring5:3.0.12 component, thymeleaf combined with specific scenarios in template injection may lead to remote code execution.