==========================================================================
Ubuntu Security Notice USN-6881-1
July 08, 2024
exim4 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:
Exim could be made to allow response injection if it received a specially
crafted response.
Software Description:
- exim4: Exim is a mail transport agent
Details:
It was discovered that Exim did not enforce STARTTLS sync point on client
side. An attacker could possibly use this issue to perform response
injection during MTA SMTP sending.
Update instructions:
The problem can be corrected by updating your system to the following
package versions:
Ubuntu 20.04 LTS
   exim4                           4.93-13ubuntu1.11
   exim4-base                      4.93-13ubuntu1.11
   eximon4  4.93-13ubuntu1.11
Ubuntu 18.04 LTS
   exim4                           4.90.1-1ubuntu1.10+esm4
                                   Available with Ubuntu Pro
   exim4-base                      4.90.1-1ubuntu1.10+esm4
                                   Available with Ubuntu Pro
   eximon4                         4.90.1-1ubuntu1.10+esm4
                                   Available with Ubuntu Pro
Ubuntu 16.04 LTS
   exim4                           4.86.2-2ubuntu2.6+esm7
                                   Available with Ubuntu Pro
   exim4-base                      4.86.2-2ubuntu2.6+esm7
                                   Available with Ubuntu Pro
   eximon4                         4.86.2-2ubuntu2.6+esm7
                                   Available with Ubuntu Pro
Ubuntu 14.04 LTS
   exim4                           4.82-3ubuntu2.4+esm8
                                   Available with Ubuntu Pro
   exim4-base                      4.82-3ubuntu2.4+esm8
                                   Available with Ubuntu Pro
   eximon4                         4.82-3ubuntu2.4+esm8
                                   Available with Ubuntu Pro
In general, a standard system update will make all the necessary changes.
References:
https://ubuntu.com/security/notices/USN-6881-1 
<https://ubuntu.com/security/notices/USN-6881-1>
   CVE-2021-38371
Package Information:
https://launchpad.net/ubuntu/+source/exim4/4.93-13ubuntu1.11 
<https://launchpad.net/ubuntu/+source/exim4/4.93-13ubuntu1.11>