libheif 1.18.0 before 1.23.3 contains a heap-based buffer overflow vulnerability in unc_decoder_mixed_interleave::processTile() that allows attackers to write out of bounds by supplying chroma components with unequal bit depths. Attackers can craft a HEIF file declaring, for example, 16-bit Cb and 8-bit Cr to trigger file-controlled heap writes past the Cr plane, potentially achieving code execution in image-processing pipelines.