In ImageMagick 7.x before 7.0.8-42 and 6.x before 6.9.10-42, there is a use after free vulnerability in the UnmapBlob function that allows an attacker to cause a denial of service by sending a crafted file.
https://github.com/ImageMagick/ImageMagick6/issues/43
http://lists.opensuse.org/opensuse-security-announce/2019-11/msg00042.html
http://lists.opensuse.org/opensuse-security-announce/2019-11/msg00040.html