---
id: CVE-2026-40477
title: >-
  Thymeleaf is a server-side Java template engine for web and standalone
  environments
summary: >-
  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 expression execution mechanisms. Although the library
  provides mechanism…
severity: critical
cvss: 9
cvssVector: 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H'
cwe:
  - CWE-917
  - CWE-1336
  - CWE-917
vendor: thymeleaf
product: thymeleaf
affected:
  - thymeleaf < 3.1.4
patched:
  - thymeleaf 3.1.4
published: '2026-04-17'
updated: '2026-08-04'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-40477'
references:
  - url: >-
      https://github.com/thymeleaf/thymeleaf/security/advisories/GHSA-r4v4-5mwr-2fwr
    label: security-advisories@github.com
  - url: 'https://access.redhat.com/errata/RHSA-2026:21772'
    label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
  - url: 'https://access.redhat.com/security/cve/CVE-2026-40477'
    label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2459344'
    label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-40477.json
    label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
tags:
  - nvd
  - exploit-available
epss: 0.00851
epssPercentile: 0.56695
ingestedAt: '2026-08-05T12:47:47.693Z'
exploits:
  github: 1
  githubRepos:
    - 'https://github.com/xiaoqiMikko/thymeleaf-check'
  checkedAt: '2026-09-24T07:53:03.104Z'
exploitAvailable: true
---

## Overview

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 expression execution mechanisms. Although the library provides mechanisms to prevent expression injection, it fails to properly restrict the scope of accessible objects, allowing specific potentially sensitive objects to be reached from within a template. 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.

## Affected

- `thymeleaf < 3.1.4`

## Remediation

Upgrade past the affected range:

- `thymeleaf 3.1.4`