PatchSiren cyber security CVE debrief

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: 2026-06-11
Advisory published: 2026-06-11
Advisory updated: 2026-06-11

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.

Official resources

CVE-2026-40992 was published on 2026-06-11T07:16:27.177Z and modified on 2026-06-11T15:21:30.653Z.