CVE-2020-8794: Canonical Ubuntu Linux

Critical severity, CVSS 9.8. EPSS: 88.9% chance of exploitation in the next 30 days.

OpenSMTPD before 6.6.4 allows remote code execution because of an out-of-bounds read in mta_io in mta_session.c for multi-line replies. Although this vulnerability affects the client side of OpenSMTPD, it is possible to attack a server because the server code launches the client code during bounce handling.

Affected products

• Canonical Ubuntu Linux: version 18.04 only; version 19.10 only
• Debian Debian Linux: version 9.0 only; version 10.0 only
• Fedoraproject Fedora: version 31 only; version 32 only
• OpenSMTPD OpenSMTPD: before 6.6.4 (fixed in 6.6.4)

Published 2020-02-25. Last modified 2026-06-17.