USN-8834-1: Exim vulnerabilities

Publication date

28 September 2026

Overview

Several security issues were fixed in Exim.


Packages

  • exim4 - Exim is a mail transport agent

Details

It was discovered that Exim had an out-of-bounds write when
Proxy-Protocol was used with an attacker-controlled proxy. A remote
attacker could possibly use this issue to execute arbitrary code.
(CVE-2026-94054)

It was discovered that Exim had a use-after-free when certain
non-default TLS settings were used with GnuTLS. A remote attacker
could possibly use this issue to cause Exim to crash, resulting in
a denial of service. This issue only affected Ubuntu 26.04 LTS.
(CVE-2026-94055)

It was discovered that Exim allowed attackers to read uninitialized
data from stack memory when Proxy-Protocol was used with an
attacker-controlled proxy. A remote attacker could possibly use this
issue to obtain sensitive information. (CVE-2026-94056)

It was discovered that Exim allowed SMTP smuggling via crafted...

It was discovered that Exim had an out-of-bounds write when
Proxy-Protocol was used with an attacker-controlled proxy. A remote
attacker could possibly use this issue to execute arbitrary code.
(CVE-2026-94054)

It was discovered that Exim had a use-after-free when certain
non-default TLS settings were used with GnuTLS. A remote attacker
could possibly use this issue to cause Exim to crash, resulting in
a denial of service. This issue only affected Ubuntu 26.04 LTS.
(CVE-2026-94055)

It was discovered that Exim allowed attackers to read uninitialized
data from stack memory when Proxy-Protocol was used with an
attacker-controlled proxy. A remote attacker could possibly use this
issue to obtain sensitive information. (CVE-2026-94056)

It was discovered that Exim allowed SMTP smuggling via crafted data
sent after a rejection during DATA processing. A remote attacker
could possibly use this issue to inject arbitrary email messages.
(CVE-2026-94057)


Update instructions

In general, a standard system update will 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
26.04 LTS resolute exim4 –  4.99.1-1ubuntu1.5
24.04 LTS noble exim4 –  4.97-4ubuntu4.8
22.04 LTS jammy exim4 –  4.95-4ubuntu2.12

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