CVE-2026-40992 — spring-boot-starter-mail
MEDIUMCVE-2026-40992 is a medium-severity (CVSS 5) CWE-295 vulnerability in org.springframework.boot:spring-boot-starter-mail. A fix is available for org.springframework.boot:spring-boot-starter-mail — see the affected versions and patch details below.
Mail Auto-Configuration Does Not Enable SSL Hostname Verification
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-40992.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2026-40992 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 382,205 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
org.springframework.boot:spring-boot-starter-mail☕org.springframework.boot:spring-boot-starter-mail☕org.springframework.boot:spring-boot-starter-mailReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.
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.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | org.springframework.boot:spring-boot-starter-mail | ≥ 4.0.0&&< 4.0.7 | 4.0.7org.springframework.boot:spring-boot-starter-mail:4.0.7 |
| ☕Maven | org.springframework.boot:spring-boot-starter-mail | ≥ 3.5.0&&< 3.5.15 | 3.5.15org.springframework.boot:spring-boot-starter-mail:3.5.15 |
| ☕Maven | org.springframework.boot:spring-boot-starter-mail | ≥ 3.4.0 | No fix |
Affected Products
spring bootvmwareDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.springframework.boot:spring-boot-starter-mail, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update org.springframework.boot:spring-boot-starter-mail to 4.0.7 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-40992 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
Frequently Asked Questions
Is CVE-2026-40992 in your dependencies?
Find it across Maven, including transitive dependencies.