USN-2933-1: Exim vulnerabilities

15 March 2016

Several security issues were fixed in Exim.

Releases

Packages

  • 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
Ubuntu 14.04
Ubuntu 12.04

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.