Heap-buffer-overflow write in FFmpeg SANM decoding due to lack of bounds-checking in old_codec48

When decoding a frame for a SANM file (ANIM v0 variant), the decoded data can be larger than the buffer allocated for it. Frames encoded with codec 48 can specify their resolution (width x height). A buffer of appropriate size is allocated depending on the resolution. This codec can encode the frame contents using a run-length encoding algorithm. There are no checks that the decoded frame fits in the allocated buffer, leading to a heap-buffer-overflow. process_frame_obj initializes the buffers based on the frame resolution: We recommend upgrading to version 8.0 or beyond.