CVE-2026-40477
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedThymeleaf 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.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceThymeleaf versions 3.1.3 and prior contain a security bypass in expression execution where the library's protections against expression injection fail to properly restrict the scope of accessible objects. An unauthenticated attacker can achieve Server-Side Template Injection (SSTI) by reaching sensitive objects through crafted template expressions when applications pass unvalidated user input directly to the template engine.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data< 3.1.4CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- High
- Privileges
- None
- User interaction
- None
- Scope
- Changed
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Identify Thymeleaf versionInspect your project dependency file (pom.xml, build.gradle, package.json) or the thymeleaf JAR manifest for the Thymeleaf version. Also check the classpath for thymeleaf-*.jar files and note the version in the filename.Affected if The installed version is 3.1.3.RELEASE or any version prior to 3.1.4
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Locate template processing codeSearch your codebase for template engine invocations such as templateEngine.process(), templateEngine.parse(), or WebContext constructions that receive request parameters. Review controller methods that handle user requests.Affected if Code passes request parameters, headers, or other user-supplied input directly to the template engine without validation
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Review template engine configurationExamine your Thymeleaf configuration (typically in a TemplateEngine bean definition) for the resolver settings, particularly any custom IStandardExpressionResolver or IExpressionObjectProvider implementations.Affected if Custom expression resolvers or expression object providers are configured that may bypass built-in protections
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Audit template files for dynamic expression usageInspect your Thymeleaf templates (*.html files with th:*) for usage of expressions like ${}, *{}, or #{} that reference request parameters or external data sources.Affected if Templates contain expressions that process unvalidated external input
You are affected if your Thymeleaf version is below 3.1.4 AND your application passes unvalidated user input directly to the template engine for processing.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scoped3.1.4
Upgrade Thymeleaf to version 3.1.4.RELEASE and ensure all user-supplied input is validated before being passed to the template engine to prevent SSTI attacks.
3.1.4.RELEASE
- 1. Identify the current Thymeleaf version by checking your project's dependency management file (pom.xml for Maven, build.gradle for Gradle) or the compiled libraries
- 2. Update the Thymeleaf dependency version to 3.1.4.RELEASE. For Maven, change the version in pom.xml: <version>3.1.4.RELEASE</version>. For Gradle, update to: implementation 'org.thymeleaf:thymeleaf:3.1.4.RELEASE'
- 3. Rebuild your project to download and compile with the new Thymeleaf version
- 4. Test the application thoroughly in a non-production environment, focusing on template rendering functionality
- 5. Validate that the expression execution protections now properly restrict accessible objects
- 6. Deploy the updated application to production
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation2.0 h
- Implementation4.0 h
- Testing4.0 h
- Review / QA2.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-40477 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-40477 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
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- Version or environment caveats, and links to real fixes
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