CBC president and CEO Hubert Lacroix sent the ominous note last Friday.
"On Monday, I informed the board that we are projecting significant financial challenges," Lacroix told staffers.
He warned that a weak advertising market, low TV ratings among 25-54-year-olds and the loss of the NHL contract "have combined to create an important revenue shortfall for the whole of CBC/Radio-Canada."
Despite receiving more than $1 billion from taxpayers, Lacroix says that's not enough.
"We are working hard to confirm the bottom line," he said in the memo. "However, it's clear that tough and more fundamental decisions will have to be made to establish a longer-term, sustainable, financial model for our corporation."
Friends of Canadian Broadcasting has renewed a call for a larger taxpayer subsidy.
On Tuesday, Friends spokesman Ian Morrison told a Senate committee that the CBC needs an extra $100 million per year over the next four years, in line with an opposition party report from 2008.
Conservative Sen. Don Plett says he's no fan of government subsidies, but added that eliminating the CBC's subsidy is probably too difficult.
"So, I don't know what the answer is, and that of course is why we're having this study - to look at that and other issues," Plett said.
The Senate Transport and Communications Committee will continue its study of CBC challenges next week with testimony from former CRTC chair Konrad von Finckenstein.