The closure of Silicon Valley Bank, First Republic Bank, and Signature Bank earlier this year were the embodiment of concern that had been building. Many commercial banks were at risk when assets were found to be wanting and not worth their official value.

Commercial real estate loans held by banks have quickly become the most recent concern. "The tight monetary environment has placed pressure on most CRE properties' collateral values and transaction volumes while structural changes in demand for office space have adversely impacted occupancy for that asset class," Fitch Ratings wrote in May. "These factors increase credit risk for banks that have CRE loan concentrations, and are expected to have an impact on asset quality in CRE loan portfolios of U.S. banks."

While Fitch was primarily focused on banks with less than $100 billion in assets as "more susceptible to deteriorating commercial real estate (CRE) fundamentals than larger banks," it's worth looking at where the larger banks stand with real estate exposure. According to a Reuters roundup of second quarter earnings announcements from financial institutions, for many it's a shaky foundation.