What is CVE-2026-40478?

CVE-2026-40478 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: 9.1/10. Published 2026-04-17.

How severe is CVE-2026-40478?

Critical severity. CVSS v3 base score is 9.1 out of 10.

RCE in Thymeleaf Org.thymeleaf:thymeleaf-spring5

CVE-2026-40478

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 mechani…

Vulnerability class: Log4Shell (CVE-2021-44228)

EPSS: 0.001 (17.6th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 9.1 (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

https://github.com/thymeleaf/thymeleaf/security/advisories/GHSA-xjw8-8c5c-9r79 (x_refsource_CONFIRM)

Frequently asked questions

What is CVE-2026-40478?: CVE-2026-40478 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: 9.1/10. Published 2026-04-17.
How severe is CVE-2026-40478?: Critical severity. CVSS v3 base score is 9.1 out of 10.