ntpd in ntp before 4.2.8p14 and 4.3.x before 4.3.100 allows remote attackers to cause a denial of service (daemon exit or system time change) by predicting transmit timestamps for use in spoofed packets. The victim must be relying on unauthenticated IPv4 time sources. There must be an off-path attacker who can query time from the victim's ntpd instance.

ntpd in ntp before 4.2.8p14 and 4.3.x before 4.3.100 allows an off-path attacker to block unauthenticated synchronization via a server mode packet with a spoofed source IP address, because transmissions are rescheduled even when a packet lacks a valid origin timestamp.

NTP through 4.2.8p12 has a NULL Pointer Dereference.

The protocol engine in ntp 4.2.6 before 4.2.8p11 allows a remote attackers to cause a denial of service (disruption) by continually sending a packet with a zero-origin timestamp and source IP address of the "other side" of an interleaved association causing the victim ntpd to reset its association.

ntpd in ntp 4.2.8p4 before 4.2.8p11 drops bad packets before updating the "received" timestamp, which allows remote attackers to cause a denial of service (disruption) by sending a packet with a zero-origin timestamp causing the association to reset and setting the contents of the packet as the most recent timestamp. This issue is a result of an incomplete fix for CVE-2015-7704.

ntpd in ntp 4.2.x before 4.2.8p7 and 4.3.x before 4.3.92 allows authenticated users that know the private symmetric key to create arbitrarily-many ephemeral associations in order to win the clock selection of ntpd and modify a victim's clock via a Sybil attack. This issue exists because of an incomplete fix for CVE-2016-1549.

The panic_gate check in NTP before 4.2.8p5 is only re-enabled after the first change to the system clock that was greater than 128 milliseconds by default, which allows remote attackers to set NTP to an arbitrary time when started with the -g option, or to alter the time by up to 900 seconds otherwise by responding to an unspecified number of requests from trusted sources, and leveraging a resulting denial of service (abort and restart).

Multiple buffer overflows in the ctl_put* functions in NTP before 4.2.8p10 and 4.3.x before 4.3.94 allow remote authenticated users to have unspecified impact via a long variable.

The MATCH_ASSOC function in NTP before version 4.2.8p9 and 4.3.x before 4.3.92 allows remote attackers to cause an out-of-bounds reference via an addpeer request with a large hmode value.

ntpd in NTP before 4.2.8p6 and 4.3.x before 4.3.90 allows remote attackers to cause a denial of service (NULL pointer dereference) via a ntpdc reslist command.

NTP before 4.2.8p6 and 4.3.x before 4.3.90, when configured in broadcast mode, allows man-in-the-middle attackers to conduct replay attacks by sniffing the network.

The read_mru_list function in NTP before 4.2.8p9 allows remote attackers to cause a denial of service (crash) via a crafted mrulist query.

NTP before 4.2.8p9 rate limits responses received from the configured sources when rate limiting for all associations is enabled, which allows remote attackers to cause a denial of service (prevent responses from the sources) by sending responses with a spoofed source address.

An exploitable vulnerability exists in the message authentication functionality of libntp in ntp 4.2.8p4 and NTPSec a5fb34b9cc89b92a8fef2f459004865c93bb7f92. An attacker can send a series of crafted messages to attempt to recover the message digest key.

A malicious authenticated peer can create arbitrarily-many ephemeral associations in order to win the clock selection algorithm in ntpd in NTP 4.2.8p4 and earlier and NTPsec 3e160db8dc248a0bcb053b56a80167dc742d2b74 and a5fb34b9cc89b92a8fef2f459004865c93bb7f92 and modify a victim's clock.

An attacker can spoof a packet from a legitimate ntpd server with an origin timestamp that matches the peer->dst timestamp recorded for that server. After making this switch, the client in NTP 4.2.8p4 and earlier and NTPSec aa48d001683e5b791a743ec9c575aaf7d867a2b0c will reject all future legitimate server responses. It is possible to force the victim client to move time after the mode has been changed. ntpq gives no indication that the mode has been switched.

An off-path attacker can cause a preemptible client association to be demobilized in NTP 4.2.8p4 and earlier and NTPSec a5fb34b9cc89b92a8fef2f459004865c93bb7f92 by sending a crypto NAK packet to a victim client with a spoofed source address of an existing associated peer. This is true even if authentication is enabled.

ntpd in NTP 4.x before 4.2.8p8 allows remote attackers to cause a denial of service (interleaved-mode transition and time change) via a spoofed broadcast packet. NOTE: this vulnerability exists because of an incomplete fix for CVE-2016-1548.

ntpd in NTP 4.x before 4.2.8p8, when autokey is enabled, allows remote attackers to cause a denial of service (peer-variable clearing and association outage) by sending (1) a spoofed crypto-NAK packet or (2) a packet with an incorrect MAC value at a certain time.

The process_packet function in ntp_proto.c in ntpd in NTP 4.x before 4.2.8p8 allows remote attackers to cause a denial of service (peer-variable modification) by sending spoofed packets from many source IP addresses in a certain scenario, as demonstrated by triggering an incorrect leap indication.