From the SUSE bug reports:

CVE-2015-8139: To prevent off-path attackers from impersonating legitimate peers, clients require that the origin timestamp in a received response packet match the transmit timestamp from its last request to a given peer. Under assumption that only the recipient of the request packet will know the value of the transmit timestamp, this prevents an attacker from forging replies.

CVE-2015-8140: The ntpq protocol is vulnerable to replay attacks. The sequence number being included under the signature fails to prevent replay attacks for two reasons. Commands that don't require authentication can be used to move the sequence number forward, and NTP doesn't actually care what sequence number is used so a packet can be replayed at any time. If, for example, an attacker can intercept authenticated reconfiguration commands that would. for example, tell ntpd to connect with a server that turns out to be malicious and a subsequent reconfiguration directive removed that malicious server, the attacker could replay the configuration command to re-establish an association to malicious server.