No they may not. That said, our free will allows us to do dumb thing, so they can if they want.
If one has only venial sins them may receive the Eucharist but sins like masturbation should be brought to the sacrament of Confession first.
If you struggle with this sin, it only means one thing: you are normal:
2515 Etymologically, concupiscence can refer to any intense form of human desire. Christian theology has given it a particular meaning: the movement of the sensitive appetite contrary to the operation of the human reason. The apostle St. Paul identifies it with the rebellion of the flesh against the spirit.(cf. Galatians 5:16,17, 24; Ephesians 2:3) Concupiscence stems from the disobedience of the first sin. It unsettles man's moral faculties and, without being in itself an offense, inclines man to commit sins. (cf. Genesis 3:11; Council of Trent: DS 1515)
2516 Because man is a composite being, spirit and body, there already exists a certain tension in him; a certain struggle of tendencies between spirit and flesh develops.
But in fact this struggle belongs to the heritage of sin. It is a consequence of sin and at the same time a confirmation of it. It is part of the daily experience of the spiritual battle:
For the Apostle it is not a matter of despising and condemning the body which with the spiritual soul constitutes man's nature and personal subjectivity. Rather, he is concerned with the morally good or bad works, or better, the permanent dispositions - virtues and vices - which are the fruit of submission (in the first case) or of resistance (in the second case) to the saving action of the Holy Spirit. For this reason the Apostle writes: "If we live by the Spirit, let us also walk by the Spirit." (John Paul II, Dominum et Vivificantem 55; cf. Galatians 5:25)
That said, the natural law tells us sexual activity is intended for married couples and
St. Paul warned about receiving the Eucharist unworthy.
Partaking of the Supper Unworthily
27 Whoever, therefore, eats the bread or drinks the cup of the Lord in an unworthy manner will be guilty of profaning the body and blood of the Lord. 28 Let a man examine himself, and so eat of the bread and drink of the cup. 29 For any one who eats and drinks without discerning the body eats and drinks judgment upon himself. 30 That is why many of you are weak and ill, and some have died. 31 But if we judged ourselves truly, we should not be judged. 32 But when we are judged by the Lord, we are chastened so that we may not be condemned along with the world.
33 So then, my brethren, when you come together to eat, wait for one another —
34 if any one is hungry, let him eat at home—lest you come together to be condemned. About the other things I will give directions when I come.
1 Corinthians 11:27-34
A priest is usually available at most Catholic parishes to hear Confessions every Saturday.
That said, remember:
The Confessional is a tribunal of mercy and healing, not of judgment. The point is not to accuse you or impose guilt; the point is to relieve guilt and apply the balm of mercy to sins so that they might be healed.
A sin is like an injury, and the priest is like a doctor.
Hope this helps,