I believe perl fixed this issue years ago (and this recent wave of discovery was based on a paper which was sent to perl maintainers long ago). Ruby fixed this issue in 1.9 before it was a big deal. I am not aware if Ruby 1.8 has backported a fix yet.

1: http://www.cs.rice.edu/~scrosby/hash/CrosbyWallach_UsenixSec...