CVE-2026-40478

CRITICAL
2026-04-15 https://github.com/thymeleaf/thymeleaf GHSA-xjw8-8c5c-9r79
Authentication Bypass
9.1
CVSS 3.1
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CVSS VectorNVD

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H
Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
None
Scope
Changed
Confidentiality
High
Integrity
High
Availability
High

DescriptionNVD

Impact

A security bypass vulnerability exists in the expression execution mechanisms of Thymeleaf up to and including 3.1.3.RELEASE. 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).

Patches

This has been fixed in Thymeleaf 3.1.4.RELEASE.

Workarounds

No workaround is available beyond ensuring applications do not pass unvalidated user input directly to the template engine. Upgrading to 3.1.4.RELEASE is strongly recommended in any case.

Credits

Thanks to Dawid Bakaj (VIPentest.com) for responsible disclosure.

AnalysisAI

A security bypass vulnerability exists in the expression execution mechanisms of Thymeleaf up to and including 3.1.3.RELEASE. 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. …

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CVE-2026-40478 vulnerability details – vuln.today
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