CVE-2020-14954: Canonical Ubuntu Linux

Medium severity, CVSS 5.9. EPSS: 2.3% chance of exploitation in the next 30 days.

Mutt before 1.14.4 and NeoMutt before 2020-06-19 have 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 man-in-the-middle attacker) and evaluates it in a TLS context, aka "response injection."

Affected products

• Canonical Ubuntu Linux: version 12.04 only; version 16.04 only; version 18.04 only; version 19.10 only; version 20.04 only
• Debian Debian Linux: version 9.0 only; version 10.0 only; version 8.0 only
• Fedoraproject Fedora: version 31 only; version 32 only
• Mutt Mutt: before 1.14.4 (fixed in 1.14.4)
• Neomutt Neomutt: before 20200619 (fixed in 20200619)
• Opensuse Leap: version 15.1 only; version 15.2 only

Published 2020-06-21. Last modified 2026-06-17.