What is the authenticity of the hadith: "There is no ghoul, but there are sa'ali" and is the addition "but there are sa'ali" present in Sahih Muslim?

The questioner is correct in negating this addition from Sahih (definition) Muslim. It has, however, appeared in the writings of Hadith (definition) commentators such as Al-Qadi Iyad, Al-Nawawi, Al-Suyuti, Al-Azim Abadi, and Al-Qari. Al-Qadi stated in Ikmal al-Mu’allim: "It was said concerning his (peace be upon him) saying, 'And no ghoul,' that it means the jinn cannot overpower anyone, mislead them, or change their state. This is supported by his (peace be upon him) statement in another hadith: 'And no ghoul, but there are sa'ali.' They said, 'The sa'ali are the sorcerers of the jinn.'" Similar statements were made by the commentators we mentioned. We have not found this hadith with this wording narrated with a chain of transmission, except in books discussing rare words (gharib). Al-Khattabi said in Gharib al-Hadith: "Al-Sa'ali: sorcerers of the jinn, plural of sa'lah. The meaning is that the ghoul cannot overpower anyone or mislead them, but among the jinn there are sorcerers, like human sorcerers, who engage in deception and illusion." This chain of transmission is mursal. Al-Hasan (definition) ibn Muhammad is Ibn Ali ibn Abi Talib, and he is one of the reliable and jurisprudent Tabi'in. And Allah knows best.