Exim could be made to crash or run programs if it received specially crafted network traffic.

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Ubuntu Security Notice USN-4141-1
September 28, 2019

exim4 vulnerability
==========================================================================

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

- Ubuntu 19.04

Summary:

Exim could be made to crash or run programs if it received specially
crafted network traffic.

Software Description:
- exim4: Exim is a mail transport agent

Details:

It was discovered that Exim incorrectly handled certain string operations.
A remote attacker could use this issue to cause Exim to crash, resulting in
a denial of service, or possibly execute arbitrary code.

Update instructions:

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

Ubuntu 19.04:
  exim4-daemon-heavy              4.92-4ubuntu1.4
  exim4-daemon-light              4.92-4ubuntu1.4

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

References:
  https://usn.ubuntu.com/4141-1
  CVE-2019-16928

Package Information:
  https://launchpad.net/ubuntu/+source/exim4/4.92-4ubuntu1.4