Is this Hadith authentic: "Every son of a fornicator is in the Fire"? Thank you.

There is no hadith with the wording "the child of zina (illegitimate child) will not enter Paradise." However, there are hadiths that disparage the child of zina, among them the hadith "the child of zina is the worst of the three [parents]," which scholars have interpreted to mean if he acts like his parents. A narration from Aisha has been reported that removes the ambiguity, stating that the hadith was said about a hypocrite who used to harm the Messenger of Allah, peace be upon him, but its chain of narration is weak. The hadiths that disparage the child of zina—if authentic—do not encompass every child of zina, and scholars have interpreted them.