CVE-2015-1798

La característica symmetric-key en la función receive en ntp_proto.c en ntpd en NTP 4.x anterior a 4.2.8p2 requiere un MAC correcto únicamente si el campo MAC tiene una longitud que no sea cero, lo que facilita a atacantes man-in-the-middle falsificar paquetes mediante la omisión del MAC.

It was found that ntpd did not check whether a Message Authentication Code (MAC) was present in a received packet when ntpd was configured to use symmetric cryptographic keys. A man-in-the-middle attacker could use this flaw to send crafted packets that would be accepted by a client or a peer without the attacker knowing the symmetric key.

The Network Time Protocol is used to synchronize a computer's time with another referenced time source. These packages include the ntpd service which continuously adjusts system time and utilities used to query and configure the ntpd service. It was found that because NTP's access control was based on a source IP address, an attacker could bypass source IP restrictions and send malicious control and configuration packets by spoofing ::1 addresses. A denial of service flaw was found in the way NTP hosts that were peering with each other authenticated themselves before updating their internal state variables. An attacker could send packets to one peer host, which could cascade to other peers, and stop the synchronization process among the reached peers.