CVE-2026-63419: OpenImageIO: IFF ZBUFFER tile read writes past caller tile buffer

OpenImageIO is a toolset for reading, writing, and manipulating image files of any image file format relevant to VFX / animation. Prior to 3.0.21.0, 3.1.16.0, and 3.2.0.3-beta1, A zbuffer-only tiled iff is exposed with a 16-bit public imagespec while the decoder retains a 32-bit internal pixel size. iffinput::readnativetile() copies according to mheader.pixelbytes() rather than imagespec::tilebytes(true), and a failed read can leave mbuf nonempty so a later call copies partially initialized data into the undersized caller buffer, resulting in a heap out-of-bounds write and memory corruption. The affected implementation is identified by src/iff.imageio/iffinput.cpp, IffInput::readnativetile(), ImageSpec::tilebytes(true), mheader.pixelbytes(), ZBUFFER, and mbuf, which define the relevant source path, functions, state, and trigger. This issue is fixed in versions 3.0.21.0, 3.1.16.0, and 3.2.0.3-beta1.