coders/mpc.c in ImageMagick before 7.0.6-1 does not enable seekable streams and thus cannot validate blob sizes, which allows remote attackers to cause a denial of service (application crash) or possibly have unspecified other impact via an image received from stdin.
https://github.com/ImageMagick/ImageMagick/issues/556
https://github.com/ImageMagick/ImageMagick/commit/b007dd3a048097d8f58949297f5b434612e1e1a3
https://github.com/ImageMagick/ImageMagick/commit/529ff26b68febb2ac03062c58452ea0b4c6edbc1