{"id":"CVE-2026-46428","summary":"lettre has TLS hostname verification disabled when using Boring TLS backend","details":"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.","aliases":["GHSA-4pj9-g833-qx53","RUSTSEC-2026-0141"],"modified":"2026-07-23T03:56:34.707274681Z","published":"2026-07-20T15:37:58.396Z","database_specific":{"cna_assigner":"GitHub_M","cwe_ids":["CWE-295"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/46xxx/CVE-2026-46428.json"},"references":[{"type":"WEB","url":"https://github.com/lettre/lettre/releases/tag/v0.11.22"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/46xxx/CVE-2026-46428.json"},{"type":"ADVISORY","url":"https://github.com/lettre/lettre/security/advisories/GHSA-4pj9-g833-qx53"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-46428"},{"type":"ADVISORY","url":"https://rustsec.org/advisories/RUSTSEC-2026-0141.html"},{"type":"FIX","url":"https://github.com/lettre/lettre/commit/f5efffc88360dbdbfcef80f465e42d5bce68ca35"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/lettre/lettre","events":[{"introduced":"0c9fc6cb71650e49abc37540a48ffcbc2fe38ee4"},{"fixed":"f5efffc88360dbdbfcef80f465e42d5bce68ca35"},{"fixed":"9b88c4ff98fd8653cb389a66f885f02efd79ee6b"}],"database_specific":{"source":["AFFECTED_FIELD","REFERENCES"],"extracted_events":[{"introduced":"0.10.1"},{"fixed":"0.11.22"}]}}],"versions":["v0.11.21","v0.11.20","v0.11.19","v0.11.18","v0.11.17","v0.11.16","v0.11.15","v0.11.14","v0.11.13","v0.11.12","v0.11.11","v0.11.10","v0.11.9","v0.11.8","v0.11.7","v0.11.6","v0.11.5","v0.11.4","v0.11.3","v0.11.2","v0.11.1","v0.11.0","v0.10.3","v0.10.2","v0.10.1"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-46428.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:L/SI:L/SA:N"}]}