Weak Diffie-Hellman Handshake Due To Truncated Secret Length

libssh2 is vulnerable to weak handshakes. The vulnerability happens because diffiehellmansha256 function in kex.c in libssh2 generates secret key of length 128 or 256 bits instead of 1023 or 2047 bits, allowing the attackers to intercept or decrypt SSH sessions using bits/bytes confusion bug...