CVE-2026-40992
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedSpring 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.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceSpring Boot's Mail auto-configuration fails to enable hostname verification for SMTP SSL connections by default, potentially allowing man-in-the-middle attacks on mail communications. This affects all applications using the default configuration, while those explicitly setting spring.mail.properties.mail.smtp.ssl.checkserveridentity=true are protected.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Adjacent
- Complexity
- High
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- Low
- Integrity
- Low
- Availability
- Low
CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Identify Spring Boot versionInspect your project's build file (pom.xml, build.gradle) or the spring-boot-dependencies BOM to determine the Spring Boot version in useAffected if Running an unpatched Spring Boot version that has this vulnerability
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Confirm Spring Mail dependencyCheck if spring-boot-starter-mail or javax.mail/mail dependencies are included in your project's build configurationAffected if Spring Mail auto-configuration is present in the classpath
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Check for SMTP configurationSearch configuration files (application.properties, application.yml, or externalized config) for mail-related properties such as spring.mail.host, spring.mail.port, or mail.smtp settingsAffected if SMTP mail is configured and in use
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Inspect hostname verification settingLook for the property spring.mail.properties.mail.smtp.ssl.checkserveridentity in any configuration source and verify its valueAffected if The property is absent or set to false, leaving hostname verification disabled
A user is affected if they run a vulnerable Spring Boot version with Spring Mail on the classpath and have SMTP configured without setting checkserveridentity to true.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scopedSet the property spring.mail.properties.mail.smtp.ssl.checkserveridentity=true in application configuration, or upgrade to a patched Spring Boot version once released.
Spring Boot 4.0.7, 3.5.15, or 3.4.17 (or later)
- Option 1 - Configuration workaround (immediate): Add the following property to your application.properties or application.yml: spring.mail.properties.mail.smtp.ssl.checkserveridentity=true
- Option 2 - Upgrade to fixed version: Update your Spring Boot version to the next patch release for your branch
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation1.0 h
- Implementation1.0 h
- Testing2.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,376.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-40992 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-40992 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
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