The states with the biggest drops were Rhode Island (3.5 percent) and Illinois (2.3 percent).
CoreLogic's price index is based on repeat sales of the same homes and tracks their price changes over time.
Several reports last month showed that the housing market is improving, though from depressed levels.
Home builders started construction on new homes and apartments at the fastest pace in more than four years in September. They also requested the most building permits in four years, a sign that many are confident that home sales gains will continue.
New home sales jumped last month to the highest annual pace in the past two and a half years. Sales of previously occupied homes dipped in September but have risen steadily in the past year.
Sales of both new and previously occupied homes are still below levels that are consistent with a healthy housing market. That's partly because the supply of available homes for sale remains low. And many prospective home buyers are struggling to qualify for a mortgage or scrape together the bigger down payments that many banks are requiring.