Warner Bros. Discovery, Inc. plans to split its high-growth streaming and struggling network segments to unlock value and improve cash flow and debt management.

The owner of CNN and HBO Max, Warner Bros Discovery, says it will split into two companies by the middle of next year.

Moody’s Ratings has downgraded debt issued by units of Warner Bros. Discovery Inc., adding another complication to the media giant’s discussions with bondholders after it announced plans to split in t...