Shares of Yahoo spiked more than 6% in afternoon trading Tuesday as a CNBC report said that billionaire activist Carl Icahn is “mulling” the idea of leading a shareholder revolt to oust the company’s board of directors.

“There’s every chance in the world that the stock is being influenced by the speculation of Carl Icahn,” said S&P Internet analyst Scott Kessler.

Yahoo’s board has come under fire from shareholders since Microsoft (MSFT) walked away from the $47.5 billion deal. Should Icahn lead an activist charge and convince enough shareholders that he can nominate a slate that would favor a sale to Microsoft, the move could signal Microsoft to resurrect its offer to buy Yahoo (YHOO).

A call placed to Icahn’s office was not immediately returned.

Icahn would need at least a 5% stake of Yahoo’s shares to run a proxy fight. Some major Yahoo shareholders have signaled they’d be willing to back a hedge fund activist to lead a campaign to bring Microsoft back. Microsoft raised its offer from $31 to $33 in the final days before walking away.

“If I were an activist, the first call I’d make would be to Microsoft and make sure that offer of $33 would still be available,” Kessler said.

During the three-month saga, Microsoft CEO Steve Ballmer threatened to go hostile and launch a proxy fight to remove Yahoo’s board if the company didn’t accept its offer of $33 a share. Then on May 3, Ballmer withdrew the offer and said the company planned to pursue alternatives to beef up its online advertising business. Last week, Microsoft also released the proxy firm it had hired to go after Yahoo.

The deadline for Icahn or any other activist to run an alternate slate of directors is May 15.