# CVE-2025-59937: go-mail has insufficient address encoding when passing mail addresses to the SMTP client

> Attackers can manipulate SMTP commands via crafted email addresses, potentially causing wrong routing or parameter smuggling in applications using this Go library.

- **Severity:** High 8.2 (`CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 29 Sep 2025
- **Updated:** 30 Sep 2025
- **Also known as:** GHSA-wpwj-69cm-q9c5, GO-2025-3988

## What is CVE-2025-59937?

CVE-2025-59937 is a high-severity vulnerability in wneessen go-mail, published on 29 Sep 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

go-mail is a comprehensive library for sending mails with Go. In versions 0.7.0 and below, due to incorrect handling of the mail.Address values when a sender- or recipient address is passed to the corresponding MAIL FROM or RCPT TO commands of the SMTP client, there is a possibility of wrong address routing or even ESMTP parameter smuggling. For successful exploitation, it is required that the user's code allows for arbitrary mail address input (i. e. through a web form or similar). If only static mail addresses are used (i. e. in a config file) and the mail addresses in use do not consist of quoted local parts, this should not affect users. This issue is fixed in version 0.7.1

Weakness: CWE-88 (Improper Neutralization of Argument Delimiters in a Command)

## Which versions are affected by CVE-2025-59937?

3 open source packages ship an affected version, including github.com/wneessen/go-mail. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `github.com/wneessen/go-mail` | Go | All versions | 0.7.1 |
| `github.com/wneessen/go-mail` | Go | All versions | 0.7.1 |
| `github.com/wneessen/go-mail` | Go | All versions | 0.7.1 |

Products: Pebcak Go-Mail.

## How do I fix CVE-2025-59937?

Upgrade github.com/wneessen/go-mail to 0.7.1 or later.

## Is CVE-2025-59937 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2025-59937 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-59937 and fix it if it is affected.

What it is: CVE-2025-59937 is a high-severity vulnerability in wneessen go-mail, published on 29 Sep 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2025-59937 exists.

Affected packages and fixed versions:
- github.com/wneessen/go-mail (Go): affected all versions; fixed in 0.7.1
- github.com/wneessen/go-mail (Go): affected all versions; fixed in 0.7.1
- github.com/wneessen/go-mail (Go): affected all versions; fixed in 0.7.1

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-2025-59937/ (Markdown: https://insights.sbomify.com/CVE-2025-59937/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-59937
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-59937
- OSV: https://osv.dev/vulnerability/CVE-2025-59937

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-59937/
Summaries are generated and may contain mistakes; the official description above is the record.