Customers across the three banks have lost a combined $870 million since Zelle launched in 2017, regulators claim.

"Zelle became a gold mine for fraudsters, while often leaving victims to fend for themselves," the CFPB said.

In addition to exposing customers to fraud, the banks violated federal laws for electronic fund transfers, according to the suit. It said Bank of America and Chase sent customers’ transfers to the wrong recipient because of errors and inaccuracies in Zelle’s network directory.