Widely used Thymeleaf library; unauthenticated SSTI with potential code/data exposure across many Java web apps.
CVE-2026-40477
SSTI in Thymeleaf ≤3.1.3 allows unauthenticated remote template access.
Is CVE-2026-40477 being exploited?
Not confirmed. CVE-2026-40477 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 0.85% probability of exploitation in the next 30 days.
How severe is CVE-2026-40477?
CVE-2026-40477 is rated Critical. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-40477?
Yes. A fix has been recorded for CVE-2026-40477. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-40477 affect?
CVE-2026-40477 affects Thymeleaf (Java template engine) <= 3.1.3.RELEASE. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-40477?
Upgrade to 3.1.4.RELEASE
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Unauthenticated SSTI can bypass protections to access sensitive server-side objects, enabling data exposure or code execution via templates.
Immediate action required
- affected< 3.1.4.RELEASE
- affected< 3.1.4.RELEASE
- affected< 3.1.4.RELEASE
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.