# Improper restriction of the scope of accessible objects in Thymeleaf expressions

Advisory record · `GHSA-r4v4-5mwr-2fwr`

- **Identifiers:** `GHSA-r4v4-5mwr-2fwr` · `CVE-2026-40477`
- **State:** Confirmed
- **Severity:** CVSS 9.1 Critical
- **Critical:** Yes: CVSS 9+
- **Weakness (CWE):** [CWE-917](https://cwe.mitre.org/data/definitions/917.html) · [CWE-1336](https://cwe.mitre.org/data/definitions/1336.html)
- **Tags:** [Code injection](https://agentprime.io/advisories/tag/code-injection.md)
- **Published:** 15 Apr 2026
- **Updated:** 5 May 2026
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 15 Apr 2026, 19:46 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Critical

Critical, because:

- CVSS score 9.1: 9.0 or more.

How we decide what’s critical: <https://agentprime.io/advisories/critical.md>

## Affected packages

- `org.thymeleaf:thymeleaf` (Maven): affected `<3.1.4.RELEASE`; fixed in `3.1.4.RELEASE`
- `org.thymeleaf:thymeleaf-spring5` (Maven): affected `<3.1.4.RELEASE`; fixed in `3.1.4.RELEASE`
- `org.thymeleaf:thymeleaf-spring6` (Maven): affected `<3.1.4.RELEASE`; fixed in `3.1.4.RELEASE`

## Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

> Thymeleaf (org.thymeleaf:thymeleaf, thymeleaf-spring5 and thymeleaf-spring6) versions before 3.1.4.RELEASE are affected. An unauthenticated remote attacker can bypass the library's expression protections when an application passes unvalidated user input directly to the template engine, which allows server-side template injection. Upgrade to 3.1.4.RELEASE; the source lists no workaround other than avoiding passing unvalidated input to the template engine.

Written 3 Nov 2026.

## Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

## Severity and exploitation

- 9.1 Critical, CVSS 3.1: `CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H`, from CNA (GitHub_M)

- **CISA KEV:** Not listed.
- **EPSS:** 0.0085, the 58th percentile, on 11 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

## Timeline

- 31 Oct 2026, 14:20 UTC: First seen by agentprime
- 31 Oct 2026, 14:20 UTC: [Confirmed by OSV](https://osv.dev/vulnerability/GHSA-r4v4-5mwr-2fwr)

## Sources

- [GitHub Advisory Database: GHSA-r4v4-5mwr-2fwr](https://github.com/advisories/GHSA-r4v4-5mwr-2fwr)
- [OSV: GHSA-r4v4-5mwr-2fwr](https://osv.dev/vulnerability/GHSA-r4v4-5mwr-2fwr)
- <https://github.com/thymeleaf/thymeleaf/security/advisories/GHSA-r4v4-5mwr-2fwr>
- <https://nvd.nist.gov/vuln/detail/CVE-2026-40477>
- <https://github.com/thymeleaf/thymeleaf>

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.

## Check whether this affects you

A Match means an installed version is in the affected range above. Most don’t affect the app; agentprime hasn’t analysed this one yet.

- With the agentprime MCP server (<https://api.agentprime.io/mcp>), ask your agent to check the project: `check_lockfile` sends a lockfile, `check_packages` a list of installed packages, and both return the Matches and the upgrades that clear them. `get_advisory` returns this record. Setup: <https://agentprime.io/mcp.md>
- In a browser: <https://agentprime.io/check/> reads your lockfile in the browser, never uploading it.
- Whether it touches your code, with file and line: the Claude Code plugin, <https://agentprime.io/plugin.md>
- As JSON: <https://api.agentprime.io/v1/advisories/GHSA-r4v4-5mwr-2fwr>, or `POST https://api.agentprime.io/v1/match` with your packages (<https://agentprime.io/api.md>)

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The web page: <https://agentprime.io/advisories/GHSA-r4v4-5mwr-2fwr/>. Everything for agents: <https://agentprime.io/llms.txt>.