Widely used Spring Boot; default security misconfig exposes endpoints across apps; high-impact.
CVE-2026-40976
Spring Boot default web security flaw exposes all endpoints.
Is CVE-2026-40976 being exploited?
Not confirmed. CVE-2026-40976 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 0.49% probability of exploitation in the next 30 days.
How severe is CVE-2026-40976?
CVE-2026-40976 is rated Critical with a CVSS score of 9.1. 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-2026-40976?
Yes. A fix has been recorded for CVE-2026-40976. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-40976 affect?
CVE-2026-40976 affects Spring Boot 4.0.0–4.0.5, Servlet-based web apps using default security chain, spring-boot-actuator-autoconfigure dependency. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-40976?
Upgrade to Spring Boot 4.0.6 or later
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Unauthorized access to all endpoints in servlet-based apps using default security chain and actuator-autoconfigure.
Immediate action required
- affected>= 4.0.0 and < 4.0.6
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.