Last week, Moody's Analytics pointed out that moderate changes to office cap rates and cash flows could cause big problems. This week, the company digs in more to recognize that a threat for CRE isn't uniform and the question those in the industry should look at is vulnerability and how much sway concerns with banks could hold.

For example, there is the number that $2.3 trillion in commercial real estate debt is held by "small" banks. First, says Moody's, look at the entire field of CRE financing. The firm built up and then whittled down the totals, looking at Mortgage Banker Association estimates, and ended with $1.75 trillion of income-producing real estate held by FDIC-insured entities.

If one expands the number of "large" banks beyond the top 25 and add regional banks with more than $10 billion in assets but less than $160 billion, together they would hold almost 70% of CRE loans. But for smaller banks, CRE loans are 13% of total assets, while they are 4% of the largest 25 banks.