static void rpza_decode_stream(RpzaContext *s)
{
    int width = s->avctx->width;
    int stride = s->frame.linesize[0] / 2;
    int row_inc = stride - 4;
    int stream_ptr = 0;
    int chunk_size;
    unsigned char opcode;
    int n_blocks;
    unsigned short colorA = 0, colorB;
    unsigned short color4[4];
    unsigned char index, idx;
    unsigned short ta, tb;
     unsigned short *pixels = (unsigned short *)s->frame.data[0];
 
     int row_ptr = 0;
    int pixel_ptr = 0;
     int block_ptr;
     int pixel_x, pixel_y;
     int total_blocks;

    /* First byte is always 0xe1. Warn if it's different */
    if (s->buf[stream_ptr] != 0xe1)
        av_log(s->avctx, AV_LOG_ERROR, "First chunk byte is 0x%02x instead of 0xe1\n",
            s->buf[stream_ptr]);

    /* Get chunk size, ingnoring first byte */
    chunk_size = AV_RB32(&s->buf[stream_ptr]) & 0x00FFFFFF;
    stream_ptr += 4;

    /* If length mismatch use size from MOV file and try to decode anyway */
    if (chunk_size != s->size)
        av_log(s->avctx, AV_LOG_ERROR, "MOV chunk size != encoded chunk size; using MOV chunk size\n");

    chunk_size = s->size;

    /* Number of 4x4 blocks in frame. */
    total_blocks = ((s->avctx->width + 3) / 4) * ((s->avctx->height + 3) / 4);

    /* Process chunk data */
    while (stream_ptr < chunk_size) {
        opcode = s->buf[stream_ptr++]; /* Get opcode */

        n_blocks = (opcode & 0x1f) + 1; /* Extract block counter from opcode */

        /* If opcode MSbit is 0, we need more data to decide what to do */
        if ((opcode & 0x80) == 0) {
            colorA = (opcode << 8) | (s->buf[stream_ptr++]);
            opcode = 0;
            if ((s->buf[stream_ptr] & 0x80) != 0) {
                /* Must behave as opcode 110xxxxx, using colorA computed
                 * above. Use fake opcode 0x20 to enter switch block at
                 * the right place */
                opcode = 0x20;
                n_blocks = 1;
            }
        }

        switch (opcode & 0xe0) {

        /* Skip blocks */
        case 0x80:
            while (n_blocks--) {
              ADVANCE_BLOCK();
            }
            break;

        /* Fill blocks with one color */
        case 0xa0:
             colorA = AV_RB16 (&s->buf[stream_ptr]);
             stream_ptr += 2;
             while (n_blocks--) {
                 block_ptr = row_ptr + pixel_ptr;
                 for (pixel_y = 0; pixel_y < 4; pixel_y++) {
                     for (pixel_x = 0; pixel_x < 4; pixel_x++){
                        pixels[block_ptr] = colorA;
                        block_ptr++;
                     }
                     block_ptr += row_inc;
                 }
                ADVANCE_BLOCK();
             }
             break;
 
        /* Fill blocks with 4 colors */
        case 0xc0:
            colorA = AV_RB16 (&s->buf[stream_ptr]);
            stream_ptr += 2;
        case 0x20:
            colorB = AV_RB16 (&s->buf[stream_ptr]);
            stream_ptr += 2;

            /* sort out the colors */
            color4[0] = colorB;
            color4[1] = 0;
            color4[2] = 0;
            color4[3] = colorA;

            /* red components */
            ta = (colorA >> 10) & 0x1F;
            tb = (colorB >> 10) & 0x1F;
            color4[1] |= ((11 * ta + 21 * tb) >> 5) << 10;
            color4[2] |= ((21 * ta + 11 * tb) >> 5) << 10;

            /* green components */
            ta = (colorA >> 5) & 0x1F;
            tb = (colorB >> 5) & 0x1F;
            color4[1] |= ((11 * ta + 21 * tb) >> 5) << 5;
            color4[2] |= ((21 * ta + 11 * tb) >> 5) << 5;

            /* blue components */
            ta = colorA & 0x1F;
            tb = colorB & 0x1F;
            color4[1] |= ((11 * ta + 21 * tb) >> 5);
            color4[2] |= ((21 * ta + 11 * tb) >> 5);

             if (s->size - stream_ptr < n_blocks * 4)
                 return;
             while (n_blocks--) {
                 block_ptr = row_ptr + pixel_ptr;
                 for (pixel_y = 0; pixel_y < 4; pixel_y++) {
                     index = s->buf[stream_ptr++];
                    for (pixel_x = 0; pixel_x < 4; pixel_x++){
                        idx = (index >> (2 * (3 - pixel_x))) & 0x03;
                        pixels[block_ptr] = color4[idx];
                        block_ptr++;
                     }
                     block_ptr += row_inc;
                 }
                ADVANCE_BLOCK();
             }
             break;
 
         /* Fill block with 16 colors */
         case 0x00:
             if (s->size - stream_ptr < 16)
                 return;
             block_ptr = row_ptr + pixel_ptr;
             for (pixel_y = 0; pixel_y < 4; pixel_y++) {
                 for (pixel_x = 0; pixel_x < 4; pixel_x++){
                    /* We already have color of upper left pixel */
                    if ((pixel_y != 0) || (pixel_x !=0)) {
                        colorA = AV_RB16 (&s->buf[stream_ptr]);
                        stream_ptr += 2;
                    }
                    pixels[block_ptr] = colorA;
                    block_ptr++;
                 }
                 block_ptr += row_inc;
             }
            ADVANCE_BLOCK();
             break;
 
         /* Unknown opcode */
        default:
            av_log(s->avctx, AV_LOG_ERROR, "Unknown opcode %d in rpza chunk."
                 " Skip remaining %d bytes of chunk data.\n", opcode,
                 chunk_size - stream_ptr);
            return;
        } /* Opcode switch */
    }
}

The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.