Google security researcher Michal Zalewski discovered that when a malformated GIF image is rendered in certain circumstances, memory is not properly initialized before use. The resulting image then uses this memory during rendering. This could allow for the a script in web content to access this unitialized memory using the <canvas> feature. 


External Reference:

http://www.mozilla.org/security/announce/2014/mfsa2014-69.html


Acknowledgements:

Red Hat would like to thank the Mozilla project for reporting this issue. Upstream acknowledges Michal Zalewski  as the original reporter.

Statement:

This issue does not affect the version of firefox and thunderbird as shipped with Red Hat Enterprise Linux 5, 6 and 7.