CVE-2026-40478
Versions 3.1.3.RELEASE and prior contain a security bypass vulnerability in the the expression execution mechanisms.
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (0.86%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
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
- 9.0 CRITICALCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H
- EPSS
- 0.86% probability · 57th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-917, CWE-1336
- Affected
- thymeleaf/thymeleaf
- Source
- security-advisories@github.com
References
- https://github.com/thymeleaf/thymeleaf/security/advisories/GHSA-xjw8-8c5c-9r79Vendor 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
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.