CVE-2026-70629: FFmpeg 3.0 < 9.0 Uninitialized Heap Memory Read in RSCC Decoder

FFmpeg versions from 3.0 up to, but not including, 9.0 contain an uninitialized heap memory read vulnerability in the native RSCC decoder (libavcodec/rscc.c) that allows attackers to disclose heap memory contents by supplying a crafted video file with a compressed tile that decompresses fewer bytes than the declared tile geometry requires. When rsccdecodeframe() calls avimagecopyplane() without validating the decompressed byte count against the tile dimensions, the unwritten suffix of the persistent intermediate buffer ctx->inflatedbuf is copied into the decoded frame, potentially exposing data from prior heap allocations or previous decoded frames in persistent decoding services.