USN-8253-1 fixed a vulnerability in Postfix. This update provides the corresponding fix for Postfix on Ubuntu 14.04 LTS, Ubuntu 16.04 LTS, Ubuntu 18.04 LTS, and Ubuntu 20.04 LTS.
Original advisory details:
Kamil Frankowicz discovered that Postfix incorrectly handled certain enhanced status codes. A remote attacker could possibly use this issue to cause Postfix to crash, resulting in a denial of service.
2.11.0-1ubuntu1.2+esm43.1.0-3ubuntu0.4+esm43.3.0-1ubuntu0.4+esm43.4.13-0ubuntu1.4+esm1