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Ubuntu 15.10, 14.04 LTS, 12.04 LTS Exim Security Advisory

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Calendar Grey March 15, 2016
Scroller Ubuntu
March 15, 2016 advisory regarding Exim security flaws in Ubuntu that enable local users to gain elevated privileges.
Several security issues were fixed in Exim.

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. (...

Read the Full Advisory

Topics%20covered

Topics Covered

security advisory security update local privilege escalation exim ubuntu mail transport agent environment filtering

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

https://ubuntu.com/security/notices/USN-2933-1

CVE-2014-2972, CVE-2016-1531

Severity
important
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Critical

March 15, 2016

Topics%20covered

Topics Covered

security advisory security update local privilege escalation exim ubuntu mail transport agent environment filtering

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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