An issue was discovered in Ruby through 2.6.7, 2.7.x through 2.7.3, and 3.x through 3.0.1. Net::IMAP does not raise an exception when StartTLS fails with an an unknown response, which might allow man-in-the-middle attackers to bypass the TLS protections by leveraging a network position between the client and the registry to block the StartTLS command, aka a "StartTLS stripping attack."
{
"sources": [
{
"imported": "2026-08-12T15:35:15.379Z",
"id": "CVE-2021-32066",
"url": "https://services.nvd.nist.gov/rest/json/cves/2.0?cveId=CVE-2021-32066",
"html_url": "https://nvd.nist.gov/vuln/detail/CVE-2021-32066",
"modified": "2026-06-17T03:52:44.373Z",
"database_specific": {
"status": "Modified"
},
"published": "2021-08-01T19:15:07.697Z"
}
],
"license": "CC-BY-4.0"
}