ImageMagick is an application suite to manipulate and convert images. It is often used as a utility backend by web applications like forums, content management systems or picture galleries.
The SetImageInfo function was found vulnerable to a format string mishandling. Daniel Kobras discovered that the handling of "%"-escaped sequences in filenames passed to the function is inadequate. This is a new vulnerability that is not addressed by GLSA 200503-11.
By feeding specially crafted file names to ImageMagick, an attacker can crash the program and possibly execute arbitrary code with the privileges of the user running ImageMagick.
There is no known workaround at this time.
All ImageMagick users should upgrade to the latest version:
# emerge --sync
# emerge --ask --oneshot --verbose ">=media-gfx/imagemagick-6.2.5.5"