RCE in Thymeleaf Org.thymeleaf:thymeleaf-Spring5
CVE-2026-40477
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.
Vulnerability class: Log4Shell (CVE-2021-44228)
EPSS: 0.009 (54.5th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 9.0 (Critical). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H.
Affected products
- Thymeleaf Org.thymeleaf:thymeleaf-spring5 — versions < 3.1.4.RELEASE
- Thymeleaf Org.thymeleaf:thymeleaf-spring6 — versions < 3.1.4.RELEASE
- Thymeleaf — versions < 3.1.4.RELEASE
Weakness classification (CWE)
References
Frequently asked questions
- What is CVE-2026-40477?
- CVE-2026-40477 is a critical-severity vulnerability in Thymeleaf Org.thymeleaf:thymeleaf-Spring5, classified under Improper Neutralization of Special Elements used in an Expression Language Statement (Expression Language Injection). CVSS score: 9.0/10. Published 2026-04-17.
- How severe is CVE-2026-40477?
- Critical severity. CVSS v3 base score is 9.0 out of 10.