# CVE-2017-15042: Information disclosure in n/a

> Go's SMTP client may send credentials in cleartext if a malicious server disables TLS, exposing usernames and passwords to attackers.

- **Severity:** Medium 5.9 (`CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 5 Oct 2017
- **Updated:** 5 Aug 2024
- **Also known as:** AZL-79072, AZL-98781, GHSA-crv5-fmcw-6rw4, GO-2021-0178, UBUNTU-CVE-2017-15042

## What is CVE-2017-15042?

CVE-2017-15042 is a medium-severity vulnerability in Golang Go, published on 5 Oct 2017. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

An unintended cleartext issue exists in Go before 1.8.4 and 1.9.x before 1.9.1. RFC 4954 requires that, during SMTP, the PLAIN auth scheme must only be used on network connections secured with TLS. The original implementation of smtp.PlainAuth in Go 1.0 enforced this requirement, and it was documented to do so. In 2013, upstream issue #5184, this was changed so that the server may decide whether PLAIN is acceptable. The result is that if you set up a man-in-the-middle SMTP server that doesn't advertise STARTTLS and does advertise that PLAIN auth is OK, the smtp.PlainAuth implementation sends the username and password.

Weakness: CWE-319 (Cleartext Transmission of Sensitive Information)

## Which versions are affected by CVE-2017-15042?

1 open source package ship an affected version, including stdlib. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `stdlib` | Go | From 1.1.0-0 | 1.8.4, 1.9.1 |

Products: Golang Go.

## How do I fix CVE-2017-15042?

Upgrade stdlib to a fixed version for your release line: 1.8.4 or 1.9.1.

## Is CVE-2017-15042 being exploited?

There is no known exploitation of CVE-2017-15042 in the wild and no public exploit code.

## Other vulnerabilities in Golang Go

- [CVE-2020-0601](https://insights.sbomify.com/CVE-2020-0601/): Microsoft Windows CryptoAPI Spoofing (high 8.1, exploited in the wild)
- [CVE-2026-27143](https://insights.sbomify.com/CVE-2026-27143/): Missing bound checks can lead to memory corruption in safe Go in cmd/compile (critical 9.8)
- [CVE-2024-24790](https://insights.sbomify.com/CVE-2024-24790/): Unexpected behavior from Is methods for IPv4-mapped IPv6 addresses in net/netip (critical 9.8)
- [CVE-2023-39320](https://insights.sbomify.com/CVE-2023-39320/): Arbitrary code execution via go.mod toolchain directive in cmd/go (critical 9.8)
- [CVE-2023-24540](https://insights.sbomify.com/CVE-2023-24540/): Improper handling of JavaScript whitespace in html/template (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2017-15042 and fix it if it is affected.

What it is: CVE-2017-15042 is a medium-severity vulnerability in Golang Go, published on 5 Oct 2017. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2017-15042 in the wild and no public exploit code.

Affected packages and fixed versions:
- stdlib (Go): affected from 1.1.0-0; fixed in 1.8.4, 1.9.1

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-2017-15042/ (Markdown: https://insights.sbomify.com/CVE-2017-15042/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2017-15042
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2017-15042
- OSV: https://osv.dev/vulnerability/CVE-2017-15042

---
From sbomify Insights: https://insights.sbomify.com/CVE-2017-15042/
Summaries are generated and may contain mistakes; the official description above is the record.