CVE-2026-40478 CRITICAL

CVE-2026-40478: Improper neutralization of specific syntax patterns for unauthorized expressions in Thymeleaf

Vendor Thymeleaf
Product thymeleaf
Weakness CWE-917
Published April 17, 2026
Last update June 30, 2026
View on NVD All CVEs

CVSS base score

9.1/10
Attack vector Network
Attack complexity High
Privileges required None
User interaction None
Confidentiality High
Integrity High

CVSS vector

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H

What the vulnerability does

01Description

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.

Key dates

02Disclosure timeline

April 17, 2026 CVE published
June 30, 2026 Record updated