[USN-2933-1] Exim vulnerabilities

[Marc Deslauriers]

==========================================================================
Ubuntu Security Notice USN-2933-1
March 15, 2016

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

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

- Ubuntu 15.10
- Ubuntu 14.04 LTS
- Ubuntu 12.04 LTS

Summary:

Several security issues were fixed in Exim.

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

Details:

It was discovered that Exim incorrectly filtered environment variables when
used with the perl_startup configuration option. If the perl_startup option
was enabled, a local attacker could use this issue to escalate their
privileges to the root user. This issue has been fixed by having Exim clean
the complete execution environment by default on startup, including any
subprocesses such as transports that call other programs. This change in
behaviour may break existing installations and can be adjusted by using two
new configuration options, keep_environment and add_environment.
(CVE-2016-1531)

Patrick William discovered that Exim incorrectly expanded mathematical
comparisons twice. A local attacker could possibly use this issue to
perform arbitrary file operations as the Exim user. This issue only
affected Ubuntu 12.04 LTS and Ubuntu 14.04 LTS. (CVE-2014-2972)

Update instructions:

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

Ubuntu 15.10:
  exim4-daemon-heavy              4.86-3ubuntu1.1
  exim4-daemon-light              4.86-3ubuntu1.1

Ubuntu 14.04 LTS:
  exim4-daemon-custom             4.82-3ubuntu2.1
  exim4-daemon-heavy              4.82-3ubuntu2.1
  exim4-daemon-light              4.82-3ubuntu2.1

Ubuntu 12.04 LTS:
  exim4-daemon-custom             4.76-3ubuntu3.3
  exim4-daemon-heavy              4.76-3ubuntu3.3
  exim4-daemon-light              4.76-3ubuntu3.3

This update introduces environment filtering, which may break certain
existing installations. After performing a standard system update, the new
keep_environment and add_environment configurations options can be used
to adjust the new behaviour.

References:
  http://www.ubuntu.com/usn/usn-2933-1
  CVE-2014-2972, CVE-2016-1531

Package Information:
  https://launchpad.net/ubuntu/+source/exim4/4.86-3ubuntu1.1
  https://launchpad.net/ubuntu/+source/exim4/4.82-3ubuntu2.1
  https://launchpad.net/ubuntu/+source/exim4/4.76-3ubuntu3.3


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