If there is an error in initializing ChaCha20 cipher with OpenSSL, an invalid error code is returned. This can happen if there is an heap exhaustion. This error is not correctly detected and could allow libssh to use partially initialized cipher context. This is caused by the mismatch of return value meaning from OpenSSL and libssh, where OpenSSL error (rv=0) aliases with SSH_OK (0) and is returned directly from the function chacha20_poly1305_set_key(). This will likely cause error somewhere down the road.