https://csd.cmu.edu/academics/bachelors/guidelines-transfer-or-dual-degree
Non-SCS students
CMU students in majors outside of SCS can apply for transfer into the Computer Science major or a dual degree in Computer Science using this online form. Students considering a transfer or dual degree are expected to earn at least a 3.6 QPA in 15-122, 15-150, 15-210, 15-213, 15-251 and 21-127, and have an overall 3.0 QPA.
https://www.reddit.com/r/ApplyingToCollege/comments/eaen5a/cmu_cs_transfer_difficulty/
According to the website I need a 3.6 gpa in 6 specific classes to be eligible to transfer. And using CMU’s unit system it looks be a min of 4 As and 2 Bs.
So yes, it is possible to transfer to CS, but its incredibly hard to achieve that.