CVE-2020-12398: Canonical Ubuntu Linux

High severity, CVSS 7.5. EPSS: 1% chance of exploitation in the next 30 days.

If Thunderbird is configured to use STARTTLS for an IMAP server, and the server sends a PREAUTH response, then Thunderbird will continue with an unencrypted connection, causing email data to be sent without protection. This vulnerability affects Thunderbird < 68.9.0.

Affected products

• Canonical Ubuntu Linux: version 16.04 only; version 18.04 only; version 19.10 only; version 20.04 only
• Mozilla Thunderbird: before 68.9.0 (fixed in 68.9.0)

Published 2020-07-09. Last modified 2026-06-17.