libheif before 1.19.6 has a NULL pointer dereference in ImageItem_Grid::get_decoder in image-items/grid.cc because a grid image can reference a nonexistent image item.
An issue was discovered in heif::Box_iref::get_references in libheif 1.4.0, allows attackers to cause a Denial of Service or possibly other unspecified impact due to an invalid memory read.
libheif 1.4.0 has a use-after-free in heif::HeifContext::Image::set_alpha_channel in heif_context.h because heif_context.cc mishandles references to non-existing alpha images.