CVE-2026-40478: Thymeleaf

Critical severity, CVSS 9.0. EPSS: 1.2% chance of exploitation in the next 30 days.

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.

Affected products

• Thymeleaf Thymeleaf: before 3.1.4 (fixed in 3.1.4)

Published 2026-04-17. Last modified 2026-08-18.