CVE-2026-84383

libheif is a HEIF and AVIF file format decoder and encoder. From 1.22.0 until 1.23.2, a crafted HEIF, HEIC, or AVIF item graph using nested iden and auxl references can make HeifPixelImage::transferchannelfromimageas() append duplicate Alpha planes with different bit depths to mstorage. HeifPixelImage::scalenearestneighbor() in libheif/image/pixelimage.cc allocates the destination Alpha plane using the first plane's 8-bit depth, then iterates a later 10-bit or 12-bit Alpha component and writes uint16t samples into the same 8-bit allocation. The output geometry controls the overflow extent and the encoded sample values control the data written, allowing a remote file processed by heifdecodeimage() to cause a heap out-of-bounds write. This issue is fixed in version 1.23.2.