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CVE-2026-40992 Spring CVE debrief

CVE-2026-40992 is a medium-severity vulnerability in Spring Boot's Mail auto-configuration. The vulnerability has a CVSS score of 5 and CVSS severity of MEDIUM. It was published on 2026-06-11T07:16:27.177Z and modified on 2026-06-11T15:21:30.653Z. The affected versions are Spring Boot 4.0.0 through 4.0.6, 3.5.0 through 3.5.14, and 3.4.0 through 3.4.16. Applications that set the relevant JavaMail property, such as spring.mail.properties.mail.smtp.ssl.checkserveridentity=true, are not affected.

Vendor
Spring
Product
Spring Boot
CVSS
MEDIUM 5
CISA KEV
Not listed in stored evidence
Original CVE published
2026-06-11
Original CVE updated
2026-09-04
Advisory published
2026-06-11
Advisory updated
2026-09-04

Who should care

Users of Spring Boot versions 4.0.0 through 4.0.6, 3.5.0 through 3.5.14, and 3.4.0 through 3.4.16 should be aware of this vulnerability and take necessary actions to mitigate it.

Technical summary

The vulnerability is caused by Spring Boot's Mail auto-configuration not enabling hostname verification. This could potentially allow for man-in-the-middle attacks.

Defensive priority

MEDIUM

Recommended defensive actions

  • Upgrade to a non-affected version of Spring Boot.
  • Set the relevant JavaMail property, such as spring.mail.properties.mail.smtp.ssl.checkserveridentity=true, to enable hostname verification.

Evidence notes

The CVE record [cve-org] and NVD detail [nvd] provide additional information about the vulnerability.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-40992 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-40992

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-40992 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-40992

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.