Is pegging(sexual act) allowed in islam?

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.

It is not permissible for the spouses to enjoy each other in the way that is mentioned in the question as this is an act which is contradictory to the Fitrah (natural disposition upon which Allaah created mankind). Indeed this act is like the act of the people of Prophet Loot (Lut), which Allaah hated and destroyed them for it. Therefore, it is an obligation for a Muslim to fear Allaah and respect His Limits. Allaah Says (what means): {These are the limits of Allah, so do not transgress them. And whoever transgresses the limits of Allaah, then such are the wrongdoers [i.e. the unjust].}[Quran 2:229].

The permissible means which Allaah legislated for the spouses to enjoy one another are enough.  For more benefit refer to Fataawa 89475 and 90583.

Allaah Knows best.