LibEtPan through 1.9.4, as used in MailCore 2 through 0.6.3 and other products, has a STARTTLS buffering issue that affects IMAP, SMTP, and POP3. When a server sends a "begin TLS" response, the client reads additional data (e.g., from a meddler-in-the-middle attacker) and evaluates it in a TLS context, aka "response injection."

Affected: Ubuntu:16.04:LTS: libetpan

It was discovered that LibEtPan incorrectly handled STARTTLS when using IMAP, SMTP and POP3. A remote attacker could possibly use this issue to perform a response injection attack. (CVE-2020-15953)