# CVE-2026-40992: Mail Auto-Configuration Does Not Enable SSL Hostname Verification

> Spring Boot mail auto-configuration fails to verify SSL hostnames, allowing man-in-the-middle attacks unless explicitly configured.

- **Severity:** Medium 5.0 (`CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 11 Jun 2026
- **Updated:** 23 Jun 2026
- **Also known as:** CLEANSTART-2026-CZ64223, ECHO-2654-53dc-59a6, GHSA-9wxp-w4px-32vh, ROOT-APP-MAVEN-CVE-2026-40992

## What is CVE-2026-40992?

CVE-2026-40992 is a medium-severity vulnerability in Spring Boot, published on 11 Jun 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official 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.

Weakness: CWE-295 (Improper Certificate Validation)

## Which versions are affected by CVE-2026-40992?

6 open source packages ship an affected version, including org.springframework.boot:spring-boot-starter-mail. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `org.springframework.boot:spring-boot-starter-mail` | Maven | From 3.4.0 to 3.4.16 | None |
| `org.springframework.boot:spring-boot-starter-mail` | Maven | From 3.4.0 to 3.4.16 | None |
| `org.springframework.boot:spring-boot-starter-mail` | Maven | From 3.5.0 | 3.5.15 |
| `org.springframework.boot:spring-boot-starter-mail` | Maven | From 3.5.0 | 3.5.15 |
| `org.springframework.boot:spring-boot-starter-mail` | Maven | From 4.0.0 | 4.0.7 |
| `org.springframework.boot:spring-boot-starter-mail` | Maven | From 4.0.0 | 4.0.7 |

Products: Vmware Spring Boot.

## How do I fix CVE-2026-40992?

Upgrade org.springframework.boot:spring-boot-starter-mail to a fixed version for your release line: 3.5.15 or 4.0.7.

## Is CVE-2026-40992 being exploited?

There is no known exploitation of CVE-2026-40992 in the wild and no public exploit code.

## Other vulnerabilities in Spring Boot

- [CVE-2023-20873](https://insights.sbomify.com/CVE-2023-20873/): Spring Boot Security Bypass with Wildcard Pattern Matching on Cloud Foundry (critical 9.8)
- [CVE-2026-40976](https://insights.sbomify.com/CVE-2026-40976/): Spring Boot's default security filter chain has no authorization rule with Actuator but without Health (critical 9.1)
- [CVE-2026-22731](https://insights.sbomify.com/CVE-2026-22731/): Authentication Bypass under Actuator Health groups paths (high 8.2)
- [CVE-2026-22733](https://insights.sbomify.com/CVE-2026-22733/): Authentication Bypass under Actuator CloudFoundry endpoints (high 8.2)
- [CVE-2022-27772](https://insights.sbomify.com/CVE-2022-27772/): Temporary Directory Hijacking to Local Privilege Escalation Vulnerability in org.springframework.boot:spring-boot (high 7.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-40992 and fix it if it is affected.

What it is: CVE-2026-40992 is a medium-severity vulnerability in Spring Boot, published on 11 Jun 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-40992 in the wild and no public exploit code.

Affected packages and fixed versions:
- org.springframework.boot:spring-boot-starter-mail (Maven): affected from 3.4.0 up to 3.4.16; no fix listed
- org.springframework.boot:spring-boot-starter-mail (Maven): affected from 3.4.0 up to 3.4.16; no fix listed
- org.springframework.boot:spring-boot-starter-mail (Maven): affected from 3.5.0; fixed in 3.5.15
- org.springframework.boot:spring-boot-starter-mail (Maven): affected from 3.5.0; fixed in 3.5.15
- org.springframework.boot:spring-boot-starter-mail (Maven): affected from 4.0.0; fixed in 4.0.7
- org.springframework.boot:spring-boot-starter-mail (Maven): affected from 4.0.0; fixed in 4.0.7

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-40992/ (Markdown: https://insights.sbomify.com/CVE-2026-40992/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-40992
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-40992
- OSV: https://osv.dev/vulnerability/CVE-2026-40992

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-40992/
Summaries are generated and may contain mistakes; the official description above is the record.