Vulnerability Description
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.
Related Weaknesses (CWE)
References
- https://github.com/lettre/lettre/commit/f5efffc88360dbdbfcef80f465e42d5bce68ca35
- https://github.com/lettre/lettre/releases/tag/v0.11.22
- https://github.com/lettre/lettre/security/advisories/GHSA-4pj9-g833-qx53
- https://rustsec.org/advisories/RUSTSEC-2026-0141.html
- https://github.com/lettre/lettre/security/advisories/GHSA-4pj9-g833-qx53
FAQ
What is CVE-2026-46428?
CVE-2026-46428 is a documented vulnerability. 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...
How severe is CVE-2026-46428?
CVSS scoring is not yet available for CVE-2026-46428. Check NVD for updates.
Is there a patch for CVE-2026-46428?
Check the references section above for vendor advisories and patch information. Review vendor security bulletins for remediation guidance.