The machine gave 11 fake bills to four customers ranging in demonination from 10 cents to $2, the Canadian Broadcasting Corp. said Thursday.
CIBC officials were investigating how the funny money got into their system.
"It clearly must have come in from maybe some of our business customers who package up their own cash," a bank spokesman said. "We're still tracking down exactly what the source was."
It's the second embarrassing problem for the banking giant in a week, the CBC said.
A West Virginia junkyard owner said he was suing CIBC because it kept faxing him private financial information about its clients. The bank said it thought the problem had been fixed two years ago.