CVE-2026-40992

Mail interception via missing hostname verification

Published Jun 11, 2026 · Updated Jun 11, 2026

Improper certificate validation in Spring Boot Mail auto-configuration allows man-in-the-middle attackers to intercept TLS mail traffic. The auto-configuration enables SSL without setting mail..ssl.checkserveridentity, so JavaMail accepts certificates for other hosts. When SSL or an SSL bundle is configured and the identity-check property is not set explicitly, attackers can read or modify mail traffic.

CVSS severity5.0
Medium
EPSS probability0.12%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper certificate validation in Spring Boot Mail auto-configuration allows man-in-the-middle attackers to intercept TLS mail traffic. The auto-configuration enables SSL without setting mail..ssl.checkserveridentity, so JavaMail accepts certificates for other hosts. When SSL or an SSL bundle is configured and the identity-check property is not set explicitly, attackers can read or modify mail traffic.

The record

CVE
CVE-2026-40992
Published
Jun 11, 2026
Updated
Jun 11, 2026
Vendor
Spring
Product
Spring Boot
Classifications
CWE-295, T1557
Attack vector
adjacent
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 11, 2026CVE publishedPublication date reported by the CVE source.
  2. Jun 11, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=3.4.0 <3.4.17
  2. Affected versionversion=3.5.0 <3.5.15
  3. Affected versionversion=4.0.0 <4.0.7

What conditions does exploitation require?

Attack vectoradjacent
Required privilegesunauthenticated

What is affected?

Spring · Spring Bootversion=3.4.0 <3.4.17; version=3.5.0 <3.5.15; version=4.0.0 <4.0.7

Published CVSS scores

5.0VMwareCVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectoradjacent
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-295Improper Certificate Validation
T1557Adversary-in-the-Middle

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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