Sandboxed Thymeleaf expressions vulnerable to improper recognition of unauthorized syntax patterns

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

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

EPSS

• CVE-2026-41901: 0.43% estimated exploitation activity in the next 30 days; percentile 36.97 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Impact A security bypass vulnerability exists in the expression execution mechanisms of Thymeleaf up to and including 3.1.4.RELEASE. Although the library provides mechanisms to avoid the execution of potentially dangerous expressions in some specific sandboxed (restricted) contexts, it fails to properly neutralize specific constructs that allow this kind of expressions to be executed. If an application developer passes to the template engine unsanitized variables that contain such expressions, and these values are used in sandboxed contexts inside the templates, these expressions can be executed achieving Server-Side Template Injection (SSTI). Patches This has been fixed in Thymeleaf 3.1.5.RELEASE. All users are advised to upgrade immediately. Workarounds No workaround is available beyond ensuring applications do not pass unvalidated/unsanitized data directly to the template engine. Upgrading to 3.1.5.RELEASE is strongly recommended in any case.

Published by the source

4 May 2026, 21:15 UTC

Last modified by the source

13 May 2026, 16:43 UTC

Source last checked

26 Oct 2026, 16:45 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-c9ph-gxww-7744

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# Patch Next advisory brief: CVE-2026-41901

Advisory: Sandboxed Thymeleaf expressions vulnerable to improper recognition of unauthorized syntax patterns
IDs: CVE-2026-41901, GHSA-c9ph-gxww-7744
Record: https://patchnext.com/advisories/cve-2026-41901 (revision 1, source checked 26 Oct 2026, 16:45 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Critical (CVSS 9.0)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: org.thymeleaf:thymeleaf-spring6 3.1.5.RELEASE; org.thymeleaf:thymeleaf 3.1.5.RELEASE; org.thymeleaf:thymeleaf-spring5 3.1.5.RELEASE. A vendor fix does not mean a deployment is fixed.

## Affected components
- Maven org.thymeleaf:thymeleaf-spring6: affected <= 3.1.4.RELEASE; fixed in 3.1.5.RELEASE
- Maven org.thymeleaf:thymeleaf: affected <= 3.1.4.RELEASE; fixed in 3.1.5.RELEASE
- Maven org.thymeleaf:thymeleaf-spring5: affected <= 3.1.4.RELEASE; fixed in 3.1.5.RELEASE

## Suggested inspection (read-only)
- Maven org.thymeleaf:thymeleaf-spring6: check the installed version with your package manager.
- Maven org.thymeleaf:thymeleaf: check the installed version with your package manager.
- Maven org.thymeleaf:thymeleaf-spring5: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on org.thymeleaf:thymeleaf-spring6, org.thymeleaf:thymeleaf, org.thymeleaf:thymeleaf-spring5.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-c9ph-gxww-7744 (GitHub-reviewed advisory GHSA-c9ph-gxww-7744 lists affected ranges: Maven org.thymeleaf:thymeleaf >=0 =0 =0 <=3.1.4.RELEASE)

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