CVE-2021-32066
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."
Date published : 2021-08-01
https://github.com/ruby/ruby/commit/a21a3b7d23704a01d34bd79d09dc37897e00922a