[USN-6939-1] Exim vulnerability

[Fabian Toepfer]

==========================================================================
Ubuntu Security Notice USN-6939-1
July 31, 2024

exim4 vulnerability
==========================================================================

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

- Ubuntu 24.04 LTS
- Ubuntu 22.04 LTS
- Ubuntu 20.04 LTS
- Ubuntu 18.04 LTS
- Ubuntu 16.04 LTS

Summary:

Exim could be made to bypass a MIME filename extension-blocking
protection mechanism if it received specially crafted input.

Software Description:
- exim4: Exim is a mail transport agent

Details:

Phillip Szelat discovered that Exim misparses multiline MIME header
filenames. A remote attacker could use this issue to bypass a MIME filename
extension-blocking protection mechanism and possibly deliver executable
attachments to the mailboxes of end users.

Update instructions:

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

Ubuntu 24.04 LTS
   exim4                           4.97-4ubuntu4.1
   exim4-base                      4.97-4ubuntu4.1
   eximon4                         4.97-4ubuntu4.1

Ubuntu 22.04 LTS
   exim4                           4.95-4ubuntu2.6
   exim4-base                      4.95-4ubuntu2.6
   eximon4                         4.95-4ubuntu2.6

Ubuntu 20.04 LTS
   exim4                           4.93-13ubuntu1.12
   exim4-base                      4.93-13ubuntu1.12
   eximon4                         4.93-13ubuntu1.12

Ubuntu 18.04 LTS
   exim4                           4.90.1-1ubuntu1.10+esm5
                                   Available with Ubuntu Pro
   exim4-base                      4.90.1-1ubuntu1.10+esm5
                                   Available with Ubuntu Pro
   eximon4                         4.90.1-1ubuntu1.10+esm5
                                   Available with Ubuntu Pro

Ubuntu 16.04 LTS
   exim4                           4.86.2-2ubuntu2.6+esm8
                                   Available with Ubuntu Pro
   exim4-base                      4.86.2-2ubuntu2.6+esm8
                                   Available with Ubuntu Pro
   eximon4                         4.86.2-2ubuntu2.6+esm8
                                   Available with Ubuntu Pro

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

References:
   https://ubuntu.com/security/notices/USN-6939-1
   CVE-2024-39929

Package Information:
   https://launchpad.net/ubuntu/+source/exim4/4.97-4ubuntu4.1
   https://launchpad.net/ubuntu/+source/exim4/4.95-4ubuntu2.6
   https://launchpad.net/ubuntu/+source/exim4/4.93-13ubuntu1.12

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