USN-6591-2: Postfix update

Publication date

31 January 2024

Overview

Postfix could allow bypass of email authentication if it received specially crafted network traffic.


Packages

  • postfix - High-performance mail transport agent

Details

USN-6591-1 fixed vulnerabilities in Postfix. A fix with less risk of
regression has been made available since the last update. This update
updates the fix and aligns with the latest configuration guidelines
regarding this vulnerability.

We apologize for the inconvenience.

Original advisory details:

Timo Longin discovered that Postfix incorrectly handled certain email line
endings. A remote attacker could possibly use this issue to bypass an email
authentication mechanism, allowing domain spoofing and potential spamming.

Please note that certain configuration changes are required to address
this issue. They are not enabled by default for backward compatibility.
Information can be found at https://www.postfix.org/smtp-smuggling.html.

USN-6591-1 fixed vulnerabilities in Postfix. A fix with less risk of
regression has been made available since the last update. This update
updates the fix and aligns with the latest configuration guidelines
regarding this vulnerability.

We apologize for the inconvenience.

Original advisory details:

Timo Longin discovered that Postfix incorrectly handled certain email line
endings. A remote attacker could possibly use this issue to bypass an email
authentication mechanism, allowing domain spoofing and potential spamming.

Please note that certain configuration changes are required to address
this issue. They are not enabled by default for backward compatibility.
Information can be found at https://www.postfix.org/smtp-smuggling.html.

Update instructions

After a standard system update, you need to set “smtpd_forbid_bare_newline = normalize” in your configuration and reload it to make all the necessary changes.

Learn more about how to get the fixes.

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

Ubuntu Release Package Version
23.10 mantic postfix –  3.8.1-2ubuntu0.2
22.04 jammy postfix –  3.6.4-1ubuntu1.3
20.04 focal postfix –  3.4.13-0ubuntu1.4
18.04 bionic postfix –  3.3.0-1ubuntu0.4+esm3  
16.04 xenial postfix –  3.1.0-3ubuntu0.4+esm3  
14.04 trusty postfix –  2.11.0-1ubuntu1.2+esm3  

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Have additional questions?

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