CVE-2026-46428
lettre has TLS hostname verification disabled when using Boring TLS backend
CVSS Score
0.0
EPSS Score
0.0%
EPSS Percentile
0th
lettre is a a mailer library for Rust. Starting in version 0.10.1 and prior to version 0.11.22, an inverted-boolean bug in lettre's `boring-tls` integration silently disables TLS hostname verification for callers using the default (strict) configuration. An on-path attacker presenting any chain-valid certificate for any domain can intercept SMTP submission, including PLAIN/LOGIN credentials and message contents, against any lettre user built with the `boring-tls` feature. Other TLS backends (`native-tls`, `rustls`) are unaffected. Version 0.11.22 patches the issue.
| CWE | CWE-295 |
| Vendor | lettre |
| Product | lettre |
| Published | Jul 20, 2026 |
Stay Ahead of the Next One
Get instant alerts for lettre lettre
Be the first to know when new unknown vulnerabilities affecting lettre lettre are published — delivered to Slack, Telegram or Discord.
Get Free Alerts →
Free · No credit card · 60 sec setup
Affected Versions
lettre / lettre
>= 0.10.1, < 0.11.22
References
github.com: https://github.com/lettre/lettre/security/advisories/GHSA-4pj9-g833-qx53 github.com: https://github.com/lettre/lettre/commit/f5efffc88360dbdbfcef80f465e42d5bce68ca35 github.com: https://github.com/lettre/lettre/releases/tag/v0.11.22 rustsec.org: https://rustsec.org/advisories/RUSTSEC-2026-0141.html