Is the Hadith prohibiting plucking the eyebrows authentic?

Yes, it is in Sahih al-Bukhari.

عَنِ ابْنِ مَسْعُودٍ رَضِيَ اللَّهُ عَنْهُ قَالَ: «لَعَنَ اللَّهُ الوَاشِمَاتِ وَالمُسْتَوْشِمَاتِ، وَالمُتَنَمِّصَاتِ وَالمُتَفَلِّجَاتِ لِلْحُسْنِ، المُغَيِّرَاتِ خَلْقَ اللَّهِ» مَا لِي لاَ أَلْعَنُ مَنْ لَعَنَهُ رَسُولُ اللَّهِ صَلَّى اللهُ عَلَيْهِ وَسَلَّمَ، وَهُوَ فِي كِتَابِ اللَّهِ

Ibn Masood  said, ‘Allah (Most High) has cursed women who tattoo others and those who get themselves tattooed, and women who have facial hair removed, and those who fashion a space between their teeth for beautification, women who seek to change the creation of Allah (Most High). Why then should I not curse those whom the Prophet ﷺ has cursed, and it is in the book of Allah (Most High). (Sahih al-Bukhari, 5943).

This Hadith is narrated multiple times in Bukhari and also narrated in Muslim. The scholars are in agreement that the Musnad Hadith narrations found in these two books are Sahih.

وأجمعت الأمة على صحة هذين الكتابين، ووجوب العمل بأحاديثهما (تهذيب الأسماء واللغات)

The Ummah is unanimously agreed that these two books are Sahih, and that their Hadith narrations must be acted upon. (Imam al-Nawawi, Tadheeb al-Ismaa wa al-Lughaat).

And Allah (Most High) Knows Best.

– Answered by Shaykh Noorud-deen (08.05.2021)

See also:

Are all Hadith in Bukhari and Muslim Sahih?

Can women pluck eyebrows?

Can men pluck facial hair or eyebrows?

See also (video):