{"id":"CVE-2026-46428","state":"PUBLISHED","title":"lettre has TLS hostname verification disabled when using Boring TLS backend","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.","publishedAt":"2026-07-20T15:37:58.396Z","updatedAt":"2026-07-21T15:49:36.495Z","severity":{"score":9.1,"label":"Critical","version":"4.0","vector":"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","source":"GitHub_M"},"assigner":"GitHub_M","products":["lettre lettre"],"affected":[{"vendor":"lettre","product":"lettre","versions":[{"version":">= 0.10.1, < 0.11.22","status":"affected"}]}],"references":["https://github.com/lettre/lettre/security/advisories/GHSA-4pj9-g833-qx53","https://github.com/lettre/lettre/commit/f5efffc88360dbdbfcef80f465e42d5bce68ca35","https://github.com/lettre/lettre/releases/tag/v0.11.22","https://rustsec.org/advisories/RUSTSEC-2026-0141.html"],"weaknesses":["CWE-295"],"ingestedAt":"2026-10-29T20:12:07.131Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/46xxx/CVE-2026-46428.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-46428","state":"PUBLISHED","datePublished":"2026-07-20T15:37:58.396Z","dateUpdated":"2026-07-21T15:49:36.495Z","assignerShortName":"GitHub_M","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateReserved":"2026-05-13T22:18:22.830Z"},"containers":{"cna":{"title":"lettre has TLS hostname verification disabled when using Boring TLS backend","descriptions":[{"lang":"en","value":"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."}],"affected":[{"vendor":"lettre","product":"lettre","versions":[{"version":">= 0.10.1, < 0.11.22","status":"affected"}]}],"references":[{"url":"https://github.com/lettre/lettre/security/advisories/GHSA-4pj9-g833-qx53","name":"https://github.com/lettre/lettre/security/advisories/GHSA-4pj9-g833-qx53","tags":["x_refsource_CONFIRM"]},{"url":"https://github.com/lettre/lettre/commit/f5efffc88360dbdbfcef80f465e42d5bce68ca35","name":"https://github.com/lettre/lettre/commit/f5efffc88360dbdbfcef80f465e42d5bce68ca35","tags":["x_refsource_MISC"]},{"url":"https://github.com/lettre/lettre/releases/tag/v0.11.22","name":"https://github.com/lettre/lettre/releases/tag/v0.11.22","tags":["x_refsource_MISC"]},{"url":"https://rustsec.org/advisories/RUSTSEC-2026-0141.html","name":"https://rustsec.org/advisories/RUSTSEC-2026-0141.html","tags":["x_refsource_MISC"]}],"metrics":[{"cvssV4_0":{"attackVector":"NETWORK","attackComplexity":"LOW","attackRequirements":"PRESENT","privilegesRequired":"NONE","userInteraction":"NONE","vulnConfidentialityImpact":"HIGH","vulnIntegrityImpact":"HIGH","vulnAvailabilityImpact":"NONE","subConfidentialityImpact":"LOW","subIntegrityImpact":"LOW","subAvailabilityImpact":"NONE","baseScore":9.1,"baseSeverity":"CRITICAL","vectorString":"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","version":"4.0"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-295","lang":"en","description":"CWE-295: Improper Certificate Validation","type":"CWE"}]}],"providerMetadata":{"shortName":"GitHub_M","orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateUpdated":"2026-07-20T15:37:58.396Z"},"source":{"advisory":"GHSA-4pj9-g833-qx53","discovery":"UNKNOWN"}},"adp":[{"title":"CISA ADP Vulnrichment","references":[{"url":"https://github.com/lettre/lettre/security/advisories/GHSA-4pj9-g833-qx53","tags":["exploit"]}],"metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-07-21T15:48:51.405919Z","id":"CVE-2026-46428","options":[{"Exploitation":"poc"},{"Automatable":"no"},{"Technical Impact":"total"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-07-21T15:49:36.495Z"}}]}}}