lettre has TLS hostname verification disabled when using Boring TLS backend

{
  "id": "e2e9e5a1f7da00e1e395611bffab6de9131bae903e90a7fa3f47d1eecaa532c2",
  "url": "https://osv.dev/vulnerability/CVE-2026-46428",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "lettre has TLS hostname verification disabled when using Boring TLS backend",
    "summary": "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.",
    "evidence": "osv:CVE-2026-46428",
    "products": [],
    "severity": "critical",
    "structured": {
      "id": "CVE-2026-46428",
      "aliases": [
        "CVE-2026-46428",
        "GHSA-4pj9-g833-qx53",
        "RUSTSEC-2026-0141"
      ],
      "metrics": [
        {
          "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"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/lettre/lettre",
              "type": "GIT",
              "events": [
                {
                  "introduced": "0c9fc6cb71650e49abc37540a48ffcbc2fe38ee4"
                },
                {
                  "fixed": "9b88c4ff98fd8653cb389a66f885f02efd79ee6b"
                },
                {
                  "fixed": "f5efffc88360dbdbfcef80f465e42d5bce68ca35"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "0.10.1"
                      },
                      {
                        "fixed": "0.11.22"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StringRangeExpression"
                  },
                  {
                    "range": [
                      {
                        "fixed": "f5efffc88360dbdbfcef80f465e42d5bce68ca35"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  },
                  {
                    "range": [
                      {
                        "fixed": "9b88c4ff98fd8653cb389a66f885f02efd79ee6b"
                      }
                    ],
                    "source": "REFERENCES_TAG",
                    "original_tag": "v0.11.22"
                  }
                ]
              }
            }
          ],
          "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"
          }
        }
      ],
      "modified": "2026-10-28T02:30:23.161250233Z",
      "provider": "osv",
      "references": [
        "https://github.com/lettre/lettre/releases/tag/v0.11.22",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/46xxx/CVE-2026-46428.json",
        "https://github.com/lettre/lettre/security/advisories/GHSA-4pj9-g833-qx53",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-46428",
        "https://rustsec.org/advisories/RUSTSEC-2026-0141.html",
        "https://github.com/lettre/lettre/commit/f5efffc88360dbdbfcef80f465e42d5bce68ca35"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-295"
        ],
        "cna_assigner": "GitHub_M",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/46xxx/CVE-2026-46428.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-46428",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 489619,
  "published_at": "2026-07-20T15:37:58.396+00:00"
}