CVE-2026-40992

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Mail SMTP SSL Hostname Verification Bypass in Spring Boot

Publication date: 2026-06-11

Last updated on: 2026-06-23

Assigner: VMware

Description

Spring Boot's Mail auto-configuration does not enable hostname verification. Applications that set the relevant JavaMail property, such as spring.mail.properties.mail.smtp.ssl.checkserveridentity=true, are not affected. Affected versions: Spring Boot 4.0.0 through 4.0.6; 3.5.0 through 3.5.14; 3.4.0 through 3.4.16.

CVSS Scores

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Meta Information

Published

2026-06-11

Last Modified

2026-06-23

Generated

2026-07-01

AI Q&A

2026-06-11

EPSS Evaluated

2026-06-30

NVD

CVE-2026-40992

EUVD

EUVD-2026-36203

Affected Vendors & Products

Vendor	Product	Version / Range
vmware	spring_boot	From 3.4.0 (inc) to 3.4.16 (inc)
vmware	spring_boot	From 3.5.0 (inc) to 3.5.14 (inc)
vmware	spring_boot	From 4.0.0 (inc) to 4.0.6 (inc)

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-295	The product does not validate, or incorrectly validates, a certificate.

Attack-Flow Graph

Executive Summary

CVE-2026-40992 is a security vulnerability in Spring Boot's Mail auto-configuration feature where SSL hostname verification is not enabled by default.

This means that when Spring Boot configures mail sending over SSL, it does not verify that the server's hostname matches the SSL certificate, which is a critical step in preventing man-in-the-middle attacks.

Applications that explicitly set the JavaMail property `spring.mail.properties.mail.smtp.ssl.checkserveridentity=true` are not affected by this vulnerability.

Impact Analysis

This vulnerability could allow an attacker to perform man-in-the-middle attacks by bypassing SSL certificate hostname verification during mail communication.

As a result, sensitive information sent via email could be intercepted or altered without detection.

The impact includes potential loss of confidentiality, integrity, and availability of email communications.

Mitigation Strategies

The primary mitigation step is to upgrade Spring Boot to a fixed version that addresses this vulnerability.

Upgrade to Spring Boot 4.0.7 (OSS) or 4.0.6.1 (Enterprise Support) for the 4.0.x series.
Upgrade to Spring Boot 3.5.15 (OSS) or 3.5.14.1 (Enterprise Support) for the 3.5.x series.
Upgrade to Spring Boot 3.4.17 (Enterprise Support) for the 3.4.x series.

No additional mitigation steps are required beyond upgrading. Applications that explicitly set the JavaMail property spring.mail.properties.mail.smtp.ssl.checkserveridentity=true are not affected.

Compliance Impact

The vulnerability in Spring Boot's Mail auto-configuration, where SSL hostname verification is not enabled by default, could potentially allow man-in-the-middle attacks by bypassing certificate validation.

Such a security weakness may impact compliance with common standards and regulations like GDPR and HIPAA, which require protection of sensitive data in transit and mandate appropriate security controls to prevent unauthorized access or interception.

However, applications that explicitly set the JavaMail property to enable hostname verification are not affected, and upgrading to fixed versions resolves the issue.

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