ImageMagick before 7.1.2-31 and before 6.9.13-56 contains a NULL pointer dereference in the PNM coder. When the coder reaches a memory (resource) limit at a specific point during processing, the failed allocation is not handled and a NULL pointer is dereferenced, which can lead to a denial of service (application crash) when processing a specially crafted or sufficiently large PNM image.