In libssh2 before 1.9.0, the function kex_method_diffie_hellman_group_exchange_sha256 _key_exchange() in the file kex.c has an integer overflow that could lead to an out-of-bounds read in the way packets are read from the server. A remote attacker who compromises a SSH server may be able to disclose sensitive information or cause a denial of service condition on the client system when a user connects to the server.