A crafted HEIC/HEIF/AVIF file with nested identity-derivation (iden) and auxiliary (auxl) item references causes HeifPixelImage::scale_nearest_neighbor() to write 16-bit samples into an 8-bit Alpha plane allocation, producing a heap buffer overflow (OOB write). The overflow size and written values are attacker-controlled via the ISOBMFF container and HEVC bitstream content. Any application using heif_decode_image() is affected. No special API options or unusual calling patterns are required. This is fixed in 1.23.2