Don't Panic: The Thymeleaf Template Injection That Only Hurts If You Let It (CVE-2026-40478)
The Thymeleaf vulnerability with a CVSS score of 9.1 grabs your attention, as it should. But before you call the cavalry and claim this as the new Log4shell, read this first. CVE-2026-40478 is a server-side template injection vulnerability in Thymeleaf. Thymeleaf is a templating engine in Java that is used for server-side webpage rendering. The sandbox that normally prevents arbitrary code execution got bypassed using a tab character. And yes, this can lead to a remote code execution if exploited.