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Ubuntu Security Notice USN-8253-2
June 03, 2026

postfix vulnerability
==========================================================================

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

- Ubuntu 20.04 LTS
- Ubuntu 18.04 LTS
- Ubuntu 16.04 LTS
- Ubuntu 14.04 LTS

Summary:

Postfix could be made to crash if it received specially crafted network
traffic.

Software Description:
- postfix: High-performance mail transport agent

Details:

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.

Update instructions:

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

Ubuntu 20.04 LTS
  postfix                         3.4.13-0ubuntu1.4+esm1
                                  Available with Ubuntu Pro

Ubuntu 18.04 LTS
  postfix                         3.3.0-1ubuntu0.4+esm4
                                  Available with Ubuntu Pro

Ubuntu 16.04 LTS
  postfix                         3.1.0-3ubuntu0.4+esm4
                                  Available with Ubuntu Pro

Ubuntu 14.04 LTS
  postfix                         2.11.0-1ubuntu1.2+esm4
                                  Available with Ubuntu Pro

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

References:
  https://ubuntu.com/security/notices/USN-8253-2
  https://ubuntu.com/security/notices/USN-8253-1
  CVE-2026-43964