net-imap: ruby: Net::IMAP: Information disclosure via man-in-the-middle attack bypassing TLS

A flaw was found in the Ruby net-imap library. When upgrading a cleartext IMAP connection to TLS using the Net::IMAPstarttls method, the library improperly handles certain responses received during STARTTLS negotiation. A man-in-the-middle MITM attacker can inject a predicted tagged OK response...