isis_clear_checksum_lifetime(void *header)
{
    struct isis_lsp_header *header_lsp = (struct isis_lsp_header *) header;

    header_lsp->checksum[0] = 0;
    header_lsp->checksum[1] = 0;
    header_lsp->remaining_lifetime[0] = 0;
    header_lsp->remaining_lifetime[1] = 0;
}

The product reads data past the end, or before the beginning, of the intended buffer.