# Don't Panic: The Thymeleaf Template Injection That Only Hurts If You Let It (CVE-2026-40478)

DevFeed: [Don't Panic: The Thymeleaf Template Injection That Only Hurts If You Let It (CVE-2026-40478)](<https://devfeed.tech/articles/don-t-panic-the-thymeleaf-template-injection-that-only-hurts-if-you-let-it-cve-2026-40478-8214.md>)

Original publisher: [Read original article](<https://snyk.io/blog/thymeleaf-injection/>)

Author: Brian Vermeer

Published: 2026-04-29T00:00:00Z

Content type: article

Language: en

Sources: [Blog RSS Feed | Snyk](<https://devfeed.tech/sources/blog-rss-feed-snyk.md>)

Topics: [Vulnerabilities](<https://devfeed.tech/topics/vulnerabilities.md>), [Security](<https://devfeed.tech/topics/security.md>)

Tags: [application-security](<https://devfeed.tech/tags/application-security.md>), [article](<https://devfeed.tech/tags/article.md>), [developer](<https://devfeed.tech/tags/developer.md>), [external](<https://devfeed.tech/tags/external.md>), [java](<https://devfeed.tech/tags/java.md>), [payload](<https://devfeed.tech/tags/payload.md>), [security](<https://devfeed.tech/tags/security.md>), [snyk-open-source](<https://devfeed.tech/tags/snyk-open-source.md>), [spring](<https://devfeed.tech/tags/spring.md>), [spring-boot](<https://devfeed.tech/tags/spring-boot.md>), [vulnerability](<https://devfeed.tech/tags/vulnerability.md>), [vulnerability-insights](<https://devfeed.tech/tags/vulnerability-insights.md>)

## AI overview

This article explains that CVE-2026-40478 is a severe Thymeleaf server-side template injection vulnerability, but exploitation depends on user-controlled input reaching Thymeleaf's expression engine. It describes the sandbox bypass, the potential for remote code execution, and misuse patterns such as dynamic templates and view resolution. It recommends patching to Thymeleaf 3.1.4 or later and auditing applications for these conditions.

## Source excerpt

CVE-2026-40478: The Thymeleaf template injection (CVSS 9.1) is conditional. Patch to 3.1.4+ immediately, and audit your code for dynamic view or template expression misuse, which is the key precondition for exploitability.