Security researcher Abhishek Arya (Inferno) of the Google Chrome Security Team used the Address Sanitizer tool to discover a use-after-free during cycle collection. This was found in interactions with the SVG content through the document object model (DOM) with animating SVG content. This leads to a potentially exploitable crash.
In general this flaw cannot be exploited through email in the Thunderbird product because scripting is disabled, but is potentially a risk in browser or browser-like contexts.
Red Hat would like to thank the Mozilla project for reporting this issue. Upstream acknowledges Abhishek Arya as the original reporter.
This issue does not affect the version of firefox and thunderbird as shipped with Red Hat Enterprise Linux 5, 6 and 7.