# CVE-2026-40992: VMware Spring Boot improper certificate validation in Mail auto-configuration

Source: https://junglewise.ai/threats/cve-2026-40992-vmware-spring-boot-improper-certificate-validation-in-mail-auto  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-06-11. Updated: 2026-09-25  
License: CC BY 4.0 with a link back

CVE-2026-40992 · Severity: medium · CVSS 5 · Published 2026-06-11

Spring Boot is a widely-used framework for building Java applications, including those that send emails. The framework's default mail configuration fails to verify that the SMTP mail server's SSL certificate matches its hostname, leaving email communications vulnerable to man-in-the-middle attacks. An attacker on the same network could intercept and read email sent by affected applications without detection. Manual configuration can work around the issue, but the default behavior is insecure.

Technologies: [VMware Spring Boot](https://junglewise.ai/threats/technologies/spring-boot). Vendors: [Maven](https://junglewise.ai/threats/vendors/maven), [VMware](https://junglewise.ai/threats/vendors/vmware).

## Quick answers

**Is CVE-2026-40992 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-40992 being exploited in the wild.

**How severe is CVE-2026-40992?** Medium severity, with a CVSS score of 5, published 11 June 2026.

**Which products and versions are affected?** org.springframework.boot:spring-boot-starter-mail (Maven) ECOSYSTEM:introduced=4.0.0,fixed=4.0.7; VMware Spring Boot 4.0.0 through 4.0.6, 4.0.0 through 4.0.6; 3.5.0 through 3.5.14; 3.4.0 through 3.4.16.

**Is there a fix for CVE-2026-40992?** Yes. org.springframework.boot:spring-boot-starter-mail (Maven): upgrade to 4.0.7 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-40992 attacked?** It is attacked from the adjacent network, in a software library.

**Am I affected by CVE-2026-40992?** Check whether you run org.springframework.boot:spring-boot-starter-mail (Maven) or VMware Spring Boot at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- org.springframework.boot:spring-boot-starter-mail (Maven): upgrade to 4.0.7 or later

  ```sh
  # set org.springframework.boot:spring-boot-starter-mail to 4.0.7 in your pom.xml or build.gradle
  ```


## Technical details

This vulnerability is a certificate validation bypass (CWE-295) in Spring Boot's mail auto-configuration. The JavaMail library supports hostname verification via the mail.smtp.ssl.checkserveridentity property, but Spring Boot does not enable this by default. An attacker with network adjacency (e.g., on the same network segment or via compromised network infrastructure) can perform a man-in-the-middle attack by presenting a valid certificate for any domain and intercepting SMTP connections. This requires high attack complexity due to network positioning but results in potential disclosure of email content and integrity compromise. Patches are available: 4.0.7, 3.5.15, and 3.4.17+.

## Affected products

- Spring Spring Boot 4.0.0 through 4.0.6
- Spring Spring Boot 3.5.0 through 3.5.14
- Spring Spring Boot 3.4.0 through 3.4.16

## Identifiers

- CVE-2026-40992
- GHSA-9wxp-w4px-32vh

## Timeline

- 2026-06-11: disclosed: Published to GitHub Advisory Database
- 2026-06-11: patched: Patches released: 4.0.7, 3.5.15

## References

- [https://spring.io/security/cve-2026-40992](https://spring.io/security/cve-2026-40992)

## Related threats

- [VMware Spring Boot insecure directory in ArtemisEmbeddedConfigurationFactory](https://junglewise.ai/threats/cve-2026-41001-vmware-spring-boot-insecure-directory-in)
- [VMware Spring Boot link resolution vulnerability in ApplicationPidFileWriter](https://junglewise.ai/threats/cve-2026-40977-vmware-spring-boot-link-resolution-vulnerability-in)
- [Spring Boot authentication bypass in default web security filter chain](https://junglewise.ai/threats/cve-2026-40976-spring-boot-authentication-bypass-in-default-web-security-filter)
- [Spring Boot weak PRNG in random value property source](https://junglewise.ai/threats/cve-2026-40975-spring-boot-weak-prng-in-random-value-property-source)
- [VMware Spring Boot Improper Certificate Validation in Cassandra auto-configuration](https://junglewise.ai/threats/cve-2026-40974-vmware-spring-boot-improper-certificate-validation-in-cassandra)