Since last Friday, shares of the digital audio company Sirius XM Holdings ( SIRI -3.06%) are now trading 13.5% lower as of 1:52 p.m. ET Thursday. Sirius, a stock Warren Buffett's Berkshire Hathaway has been piling into, fell after the company's chief financial officer (CFO) spoke about concerns for the sector.

Legendary investor Warren Buffett is sitting on nearly $200 billion in cash, signaling major concerns about the stock market. His favorite stock market indicator suggests that a 40% market crash could be imminent.

Warren Buffett is rightly called the greatest living investor. Since becoming CEO of Berkshire Hathaway (NYSE:BRK-A)(NYSE:BRK-B) in 1965, Buffett has generated cumulative returns 5,502,284%, a nearly 20% annual return,