According to the RedHat summary :
An out-of-bounds read vulnerability in CopyMagickMemory was found that can lead to memory leak because the read data are written into output image using SetImageProperty or can cause DoS by crashing the application.
Fixed by upstream as in , in version 6.9.5-4. The first version available in gentoo above that is 6.9.5-5, still keyworded as unstable.
Verified the source of media-gfx/imagemagick-18.104.22.168, which does contain the appropriate fix.
This issue was resolved and addressed in
GLSA 201611-21 at https://security.gentoo.org/glsa/201611-21
by GLSA coordinator Aaron Bauman (b-man).