curve25519 key exchange incorrectly, causing connection failures
about 0.2% of the time when this method is used against a peer that
implements the method properly.
Fix the problem and disable the curve25519 KEX when speaking to
OpenSSH 6.5 or 6.6. This version will identify itself as 6.6.1
to enable the compatability code.
openssh-6.6.1p1
Petr Lautrbach