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Vulnerability record · CVE-2026-40478 · published 17 April 2026

CVE-2026-40478: Thymeleaf expression language injection vulnerability

Thymeleaf · Thymeleaf

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.

9.0 CVSS 3.1 Critical EPSS 1.2% · top 33.0% CWE-917 · Expression language injectionCWE-1336 · CWE-1336
9.0CVSS 3.1 base score
1.2%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
5References
18 Aug 2026Last modified by NVD

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.

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

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/thymeleaf/thymeleaf/security/advisories/GHSA-xjw8-8c5c-9r79 Vendor Advisory
https://access.redhat.com/errata/RHSA-2026:21772
https://access.redhat.com/security/cve/CVE-2026-40478
https://bugzilla.redhat.com/show_bug.cgi?id=2459349
https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-40478.json

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Source: NIST National Vulnerability Database (record CVE-2026-40478), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.