Your thoughts and instincts are clouded. Stupefied always includes a value. You take a status penalty equal to this value on Intelligence-, Wisdom-, and Charisma-based checks and DCs, including Will saving throws, spell attack rolls, spell DCs, and skill checks that use these ability scores. Any time you attempt to Cast a Spell while stupefied, the spell is disrupted unless you succeed at a flat check with a DC equal to 5 + your stupefied value.