It was discovered that OpenSMTPD incorrectly verified the sender's or receiver's e-mail addresses under certain conditions. An attacker could possibly use this vulnerability to execute arbitrary commands as root. (CVE-2020-7247)
It was discovered that OpenSMTPD did not properly handle hardlinks under certain conditions. An unprivileged local attacker could possibly use this issue to obtain sensitive information. This issue only affected Ubuntu 16.04 ESM. (CVE-2020-8793)
It was discovered that OpenSMTPD mishandled certain input. A remote, unauthenticated attacker could possibly use this vulnerability to execute arbitrary shell commands as any non-root user. This issue only affected Ubuntu 16.04 ESM. (CVE-2020-8794)