Is it permissible for a wife to give up her share of inheritance without her husband’s permission?

Praise be to Allah.

A woman has the right to dispose of her wealth however she wants, if she is mature and knows what she is doing. This is the view of the majority of scholars. 

Ibn Qudamah (may Allah have mercy on him) said:  

The apparent meaning of what al-Khuraqi said is that a woman who is mature and knows what she is doing has the right to dispose of all her wealth, by giving it in charity or by buying and selling. This is one of the two views that were narrated from Ahmad, and this is also the view of Abu Haneefah, al-Shafi’i and Ibn al-Mundhir. There is another view narrated from Ahmad, which is that she does not have the right to dispose of more than one-third of her wealth for nothing in return, except with her husband’s permission. This is also the view of Malik.  

From al-Mughni, 4/299. 

See also question no. 48952 

But in the interests of a good relationship with her husband, the wife should tell him about that, especially in this case where there is the possibility that he may lose out on his rights to your brothers. 

So long as you have in fact given up your right to your inheritance, you should try now to please your husband and remind your brothers of his rights to their father’s land, and that they have no right to deny him because giving others their rights is such an important matter and consuming the wealth of others unlawfully is such a grievous sin. 

And Allah knows best.