==========================================================================
Ubuntu Security Notice USN-8382-1
June 03, 2026

exim4 vulnerabilities
==========================================================================

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:

Several security issues were fixed in Exim.

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

Details:

Timo Longin discovered that Exim incorrectly handled certain SMTP messages
in PIPELINING/CHUNKING configurations. A remote attacker could possibly use
this issue to perform SMTP smuggling. This issue only affected Ubuntu
14.04 LTS. (CVE-2023-51766)

It was discovered that Exim incorrectly handled certain malformed JSON
data in headers. A remote attacker could possibly use this issue to crash
Exim, resulting in a denial of service, or execute arbitrary code. This
issue only affected Ubuntu 20.04 LTS. (CVE-2026-40685)

It was discovered that Exim incorrectly handled certain malformed UTF-8
headers. A remote attacker could possibly use this issue to obtain
sensitive information. This issue only affected Ubuntu 20.04 LTS.
(CVE-2026-40686)

It was discovered that Exim incorrectly handled certain SPA resources.
A remote attacker could possibly use this issue to crash Exim, resulting in
a denial of service, or obtain sensitive information. This issue only
affected Ubuntu 20.04 LTS. (CVE-2026-40687)

It was discovered that Exim incorrectly handled certain CHUNKING
transfers in some GnuTLS configurations. A remote attacker could possibly
use this issue to crash Exim, resulting in a denial of service, or execute
arbitrary code. This issue only affected Ubuntu 20.04 LTS. (CVE-2026-45185)

Warisjeet Singh discovered that Exim incorrectly handled certain proxy
connections in builds with proxy support enabled. A remote attacker could
possibly use this issue to obtain sensitive information. This issue only
affected Ubuntu 16.04 LTS, Ubuntu 18.04 LTS, and Ubuntu 20.04 LTS.
(CVE-2026-48840)

Update instructions:

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

Ubuntu 20.04 LTS
  exim4                           4.93-13ubuntu1.12+esm1
                                  Available with Ubuntu Pro
  exim4-base                      4.93-13ubuntu1.12+esm1
                                  Available with Ubuntu Pro
  exim4-daemon-heavy              4.93-13ubuntu1.12+esm1
                                  Available with Ubuntu Pro
  exim4-daemon-light              4.93-13ubuntu1.12+esm1
                                  Available with Ubuntu Pro
  exim4-dev                       4.93-13ubuntu1.12+esm1
                                  Available with Ubuntu Pro
  eximon4                         4.93-13ubuntu1.12+esm1
                                  Available with Ubuntu Pro

Ubuntu 18.04 LTS
  exim4                           4.90.1-1ubuntu1.10+esm6
                                  Available with Ubuntu Pro
  exim4-base                      4.90.1-1ubuntu1.10+esm6
                                  Available with Ubuntu Pro
  exim4-daemon-heavy              4.90.1-1ubuntu1.10+esm6
                                  Available with Ubuntu Pro
  exim4-daemon-light              4.90.1-1ubuntu1.10+esm6
                                  Available with Ubuntu Pro
  exim4-dev                       4.90.1-1ubuntu1.10+esm6
                                  Available with Ubuntu Pro
  eximon4                         4.90.1-1ubuntu1.10+esm6
                                  Available with Ubuntu Pro

Ubuntu 16.04 LTS
  exim4                           4.86.2-2ubuntu2.6+esm9
                                  Available with Ubuntu Pro
  exim4-base                      4.86.2-2ubuntu2.6+esm9
                                  Available with Ubuntu Pro
  exim4-daemon-heavy              4.86.2-2ubuntu2.6+esm9
                                  Available with Ubuntu Pro
  exim4-daemon-light              4.86.2-2ubuntu2.6+esm9
                                  Available with Ubuntu Pro
  exim4-dev                       4.86.2-2ubuntu2.6+esm9
                                  Available with Ubuntu Pro
  eximon4                         4.86.2-2ubuntu2.6+esm9
                                  Available with Ubuntu Pro

Ubuntu 14.04 LTS
  exim4                           4.82-3ubuntu2.4+esm9
                                  Available with Ubuntu Pro
  exim4-base                      4.82-3ubuntu2.4+esm9
                                  Available with Ubuntu Pro
  exim4-daemon-heavy              4.82-3ubuntu2.4+esm9
                                  Available with Ubuntu Pro
  exim4-daemon-light              4.82-3ubuntu2.4+esm9
                                  Available with Ubuntu Pro
  exim4-dev                       4.82-3ubuntu2.4+esm9
                                  Available with Ubuntu Pro
  eximon4                         4.82-3ubuntu2.4+esm9
                                  Available with Ubuntu Pro

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

References:
  https://ubuntu.com/security/notices/USN-8382-1
  CVE-2023-51766, CVE-2026-40685, CVE-2026-40686, CVE-2026-40687,
  CVE-2026-45185, CVE-2026-48840