SSH Protocol Trick
Sebastian Krahmer has written a paper which describes (PDF format)
"how SSH clients can be tricked into thinking they are missing the hostkey 2 even though they already have it in their list of known keys." A shorter version of the paper appears in
PHRACK 59.
The paper and exploit program will be "uploaded
to 7350.org as soon as the issue has been 'solved' by SSH vendors
and some corrections made it into the text."