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Ubuntu Security Notice USN-6591-1
January 22, 2024

postfix vulnerability

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

• Ubuntu 23.10
• Ubuntu 22.04 LTS
• Ubuntu 20.04 LTS
• Ubuntu 18.04 LTS (Available with Ubuntu Pro)
• Ubuntu 16.04 LTS (Available with Ubuntu Pro)
• Ubuntu 14.04 LTS (Available with Ubuntu Pro)

Summary:

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

Software Description:

• postfix: High-performance mail transport agent

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 athttps://www.postfix.org/smtp-smuggling.html.

Update instructions:

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

Ubuntu 23.10:
postfix 3.8.1-2ubuntu0.1

Ubuntu 22.04 LTS:
postfix 3.6.4-1ubuntu1.2

Ubuntu 20.04 LTS:
postfix 3.4.13-0ubuntu1.3

Ubuntu 18.04 LTS (Available with Ubuntu Pro):
postfix 3.3.0-1ubuntu0.4+esm2

Ubuntu 16.04 LTS (Available with Ubuntu Pro):
postfix 3.1.0-3ubuntu0.4+esm2

Ubuntu 14.04 LTS (Available with Ubuntu Pro):
postfix 2.11.0-1ubuntu1.2+esm2

After a standard system update you need to enable
smtpd_forbid_bare_newline in your configuration and reload it to make
all the necessary changes.

References:
https://ubuntu.com/security/notices/USN-6591-1
CVE-2023-51764,https://bugs.launchpad.net/ubuntu/+source/postfix/+bug/2049337

Package Information:
https://launchpad.net/ubuntu/+source/postfix/3.8.1-2ubuntu0.1
https://launchpad.net/ubuntu/+source/postfix/3.6.4-1ubuntu1.2
https://launchpad.net/ubuntu/+source/postfix/3.4.13-0ubuntu1.3