Comment by luckman212

It seems to only affect Bash 5.3.20 (Homebrew) - very odd:

    % /bin/bash --version
    GNU bash, version 3.2.57(1)-release (arm64-apple-darwin26)
    
    % /opt/homebrew/bin/bash --version
    GNU bash, version 5.3.20(1)-release (aarch64-apple-darwin27.0.0)
    
    % zsh -c '/sbin/ifconfig en0 | grep ether'
    ether d0:11:e5:1a:27:7a
    
    % /bin/bash -c '/sbin/ifconfig en0 | grep ether'
    ether d0:11:e5:1a:27:7a
    
    % /opt/homebrew/bin/bash -c '/sbin/ifconfig en0 | grep ether'
    ether 02:00:00:00:00:00