An OpenSMTPD security update has been released for Ubuntu Linux 19.10 and 18.04 LTS.

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Ubuntu Security Notice USN-4268-1
February 05, 2020

OpenSMTPD vulnerability
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A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 19.10
- Ubuntu 18.04 LTS

Summary:

OpenSMTPD could be made to run programs as root if it received specially
crafted input over the network.

Software Description:
- opensmtpd: secure, reliable, lean, and easy-to configure SMTP server

Details:

It was discovered that OpenSMTPD incorrectly verified the sender's or
receiver's e-mail addresses under certain conditions. An attacker could use
this vulnerability to execute arbitrary commands as root.

Update instructions:

The problem can be corrected by updating your system to the following
package versions:

Ubuntu 19.10:
opensmtpd 6.0.3p1-6ubuntu0.1

Ubuntu 18.04 LTS:
opensmtpd 6.0.3p1-1ubuntu0.1

In general, a standard system update will make all the necessary changes.

References:
  https://usn.ubuntu.com/4268-1
CVE-2020-7247

Package Information:
  https://launchpad.net/ubuntu/+source/opensmtpd/6.0.3p1-6ubuntu0.1
  https://launchpad.net/ubuntu/+source/opensmtpd/6.0.3p1-1ubuntu0.1