This indicates a denial of service vulnerability in the SSH1 protocol implementation in OpenSSH.
The vulnerability is caused by improper implementation of a function in the kex module. A remote attacker may be able to exploit this to cause a denial of service condition on the affected system.
OpenSSH OpenSSH prior to revision 1.127
OpenSSH OpenSSH portable prior to version 7.4p1
Denial of Service: Remote attackers can crash vulnerable systems.
Upgrade to the latest version available from the website.