JPMorgan Chase CEO Jamie Dimon seems to be softening his tone on cryptocurrencies a bit but still remains doubtful the surge in bitcoin itself is sustainable.

"Look, everyone has a personal opinion about bitcoin. I remain highly skeptical of it," Dimon told CNBC on Friday. "But as I've said previously, I'm open-minded to uses of cryptocurrencies if properly controlled and regulated."

The latest remarks come after months of criticism from JPMorgan's top executive.

"If you're stupid enough to buy it, you'll pay the price for it one day," Dimon warned in October, when bitcoin traded around $5,800. The digital currency has since soared above $19,000 on some online exchanges and was trading around $15,620 Friday, according to CoinDesk.

Though the executive called bitcoin a "fraud" in September, he did note that the digital currency could potentially soar as high as $100,000 before topping.

"I'm not saying 'go short bitcoin and sell $100,000 of bitcoin before it goes down," he said in September. "This is not advice of what to do. My daughter bought bitcoin, it went up and now she thinks she's a genius."

To be sure, while Dimon has been a bitcoin critic, he continues to be more positive on blockchain technology.

JPMorgan Chase announced in October that it was launching a blockchain-based system with two other banks to reduce global payment transactions. The technology eliminates the need for a third party intermediary using a permanent and open record of all transactions on a network, thereby speeding transaction times.

Blockchain is "transformational for the financial services industry" and JPMorgan is "working hard [and] investing money" in it, the bank's chief financial officer, Marianne Lake, said during October's third-quarter earnings conference call.

—CNBC's Wilfred Frost and Evelyn Cheng contributed to this report.