Fitch Ratings assigned an "AAA" rating to Commonwealth Bank of Australia's (ASX:CBA) $1.5 billion Series 122 mortgage-covered bonds, with a stable outlook, according to a Wednesday statement.

The bonds are rated three notches higher than CBA's long-term issuer default rating of "AA-." Fitch's analysis relies on the committed asset percentage used in the program's asset coverage test of 95.0%, which provides more protection than Fitch's breakeven asset percentage of 97.0%, the statement said.