Read MoreVulture investor: This hot sector is 'vulnerable'
Sarah Ketterer, CEO and portfolio manager of global stock investor Causeway Capital Management, added a similar warning about so-called defensive stocks in Asia, Europe and the U.S.
Such stocks come from companies whose products and services are typically less susceptible to economic cycles, such as food staples and utilities, and are often seen as less risky investments.
"Defensives are at a huge premium," Ketterer said on the panel. "It's as if this enormous wave of artificial monetary creation has led to huge asset price inflation and it's gone to safety."
"When the volatility returns, will those stocks be as defensive as investors anticipate?" she asked. "They're trading at multiples far in excess of the market. ... Tthat is no room for error."
Read MoreBig money: 'Awfully dangerous' to take risk now
Morris Mark, founder of Mark Asset Management, offered a more benign view.
"Usually when you're in a bubble, you don't know it. You're excited about something, you're clamoring for it," Mark said. "About the only thing I see people clamoring for today is security. ... I'm not sure you'd call that a bubble."