What is the ruling on one who prays Asr three rak'ahs with two tashahhuds?

Whoever mistakenly says the tasleem in the third rak'ah must complete the remaining rak'ah if they remember it soon after. Then, they should perform the two prostrations of forgetfulness (sujud as-sahw) after the tasleem. Otherwise, their prayer becomes invalid if a long time passes customarily, or if they do not perform it at all, or if they say the tasleem before completing the prayer. The proof for this is the hadith of Imran ibn Husayn in Sahih Muslim.