When I change the value of a ComboBox all change

I have a database with two tables, Tab1 and Tab2. In Tab 1 I have Cd_Tab1 and Nm_Object. In Tab2 I have Cd_Tab2, Cd_Tab1. The two are related.
In my project I have 4 ComboBox, all should represent the value of Cd_Tab2, but each one will write a new Cd_Tab2 (Ex: First Cmb = Cd_Tab2 (1), Second Cmb = Cd_Tab2 (2) etc ...
The problem I'm having is that when I change the value of one cmb in the project all the others change together.

XAML code:

<ComboBox x:Name="btCmbAtkBaAtr2" HorizontalAlignment="Left" Margin="0,79,0,0" 
            VerticalAlignment="Top" Width="50" DisplayMemberPath="Nm_Objeto" 
            ItemsSource="{Binding Source={StaticResource Tab1ViewSource}}" 
            SelectedValuePath="Cd_Tab1" 
            SelectedValue="{Binding Cd_Tab1, Source={StaticResource Tab2ViewSource}}"/>
<ComboBox x:Name="btCmbAtkBaAtr2" HorizontalAlignment="Left" Margin="0,79,0,0" VerticalAlignment="Top" Width="50" DisplayMemberPath="Nm_Atr" ItemsSource="{Binding Source={StaticResource atributosNormaisViewSource}}" SelectedValuePath="Cd_AtributosNormais" SelectedValue="{Binding Cd_AtributosNormais, Source={StaticResource ataquesBasicosViewSource}}"/>
<ComboBox x:Name="btCmbAtkBaAtr3" HorizontalAlignment="Left" Margin="0,121,0,0" VerticalAlignment="Top" Width="50" DisplayMemberPath="Nm_Atr" ItemsSource="{Binding Source={StaticResource atributosNormaisViewSource}}" SelectedValuePath="Cd_AtributosNormais" SelectedValue="{Binding Cd_AtributosNormais, Source={StaticResource ataquesBasicosViewSource}}"/>
<ComboBox x:Name="btCmbAtkBaAtr4" HorizontalAlignment="Left" Margin="0,163,0,0" VerticalAlignment="Top" Width="50" DisplayMemberPath="Nm_Atr" ItemsSource="{Binding Source={StaticResource atributosNormaisViewSource}}" SelectedValuePath="Cd_AtributosNormais" SelectedValue="{Binding Cd_AtributosNormais, Source={StaticResource ataquesBasicosViewSource}}"/>

Tab1:

Tab2: