Protecting Against CVE-2016-3714 (ImageMagick)

Overview

A security vulnerability has been discovered in the ImageMagick software suite that can potentially allow remote code execution.

Impact

All versions of ImageMagick are affected. An updated version has been committed and should be rolling out to repositories in the near future. Until a patch is available for all systems, Liquid Web is taking steps to block the offending payloads. Additionally, a direct modification to ImageMagick’s policy file can reduce the risk of an exploit due to the vulnerability.

Resolution

A full resolution is not possible until a patch is released and applied. While that is anticipated to be available soon, in the interim, policies specifically blocking known exploits can be added directly to ImageMagick’s policy file, policy.xml. The file will be located in one of two possible directories, depending on how the software was installed:

  • /etc/ImageMagick/policy.xml
  • /usr/local/etc/ImageMagick-6/policy.xml

Once located, open policy.xml in your preferred text editor and add the following nine lines to the bottom of the file to help minimize the risks of exploit:

<policy domain="coder" rights="none" pattern="EPHEMERAL" />
<policy domain="coder" rights="none" pattern="HTTPS" />
<policy domain="coder" rights="none" pattern="MVG" />
<policy domain="coder" rights="none" pattern="MSL" />
<policy domain="coder" rights="none" pattern="TEXT" />
<policy domain="coder" rights="none" pattern="SHOW" />
<policy domain="coder" rights="none" pattern="WIN" />
<policy domain="coder" rights="none" pattern="PLT" />
<policy domain="path" rights="none" pattern="@*" />

Note: This post has been updated to reflect policies for four additional coders identified as potentially vulnerable, and one that prevents indirect reads entirely. ImageMagick still should be upgraded when the latest release is made available even if the policy file has been manually edited.

Managed customers who need help editing the policy file may contact Heroic Support® for assistance.