CVSS 4.0
9.1 criticalCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:L/SI:L/SA:NCVE-2026-46428
Critical (9.1). EPSS 0.3% chance of exploitation in the next 30 days. Fixed in lettre 0.11.22.
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.
Severity
- EPSS
- 0.3% chance of exploitation in the next 30 days; higher than 24% of CVEs (scores of 2026-10-31)
- CWE
- CWE-295
- Published
- Modified
- Record from
- the NVD, synced
Packages (OSV)
| Advisory | Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|---|
| GHSA-4pj9-g833-qx53 | crates.io | lettre | >=0.10.1 <0.11.22 | 0.11.22 |
| RUSTSEC-2026-0141 | crates.io | lettre | >=0.10.1 <0.11.22 | 0.11.22 |
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