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.
History

Mon, 20 Apr 2026 17:15:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}


Mon, 20 Apr 2026 15:15:00 +0000

Type Values Removed Values Added
First Time appeared Thymeleaf
Thymeleaf org.thymeleaf:thymeleaf-spring5
Thymeleaf org.thymeleaf:thymeleaf-spring6
Thymeleaf thymeleaf
Vendors & Products Thymeleaf
Thymeleaf org.thymeleaf:thymeleaf-spring5
Thymeleaf org.thymeleaf:thymeleaf-spring6
Thymeleaf thymeleaf

Fri, 17 Apr 2026 22:15:00 +0000

Type Values Removed Values Added
Description 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.
Title Improper neutralization of specific syntax patterns for unauthorized expressions in Thymeleaf
Weaknesses CWE-1336
CWE-917
References
Metrics cvssV3_1

{'score': 9.1, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H'}


cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-04-20T16:17:11.654Z

Reserved: 2026-04-13T19:50:42.113Z

Link: CVE-2026-40478

cve-icon Vulnrichment

Updated: 2026-04-20T16:17:07.750Z

cve-icon NVD

Status : Awaiting Analysis

Published: 2026-04-17T22:16:33.650

Modified: 2026-04-20T19:03:07.607

Link: CVE-2026-40478

cve-icon Redhat

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