In libvips before 8.6.3, a NULL function pointer dereference vulnerability was found in the vips_region_generate function in region.c, which allows remote attackers to cause a denial of service or possibly have unspecified other impact via a crafted image file. This occurs because of a race condition involving a failed delayed load and other worker threads.
https://lists.debian.org/debian-lts-announce/2018/03/msg00009.html
https://github.com/jcupitt/libvips/issues/893
https://github.com/jcupitt/libvips/commit/20d840e6da15c1574b3ed998bc92f91d1e36c2a5