Packed meat unrefrigerated storage I have a 1kg beef brisket, still in store packaging, sitting at room temp for 24 hours. Is it safe?
No it is not safe it has exceeding USDA time and temperature guidelines.

See the following for guidelines

http://www.fsis.usda.gov/wps/portal/fsis/topics/food-safety-education/get-answers/food-safety-fact-sheets/safe-food-handling/danger-zone-40-f-140-f/ct_index