dhclient in ISC DHCP 3.0.x through 4.2.x before 4.2.1-P1, 3.1-ESV before 3.1-ESV-R1, and 4.1-ESV before 4.1-ESV-R2 allows remote attackers to execute arbitrary commands via shell metacharacters in a hostname obtained from a DHCP message, as demonstrated by a hostname that is provided to dhclient-script.
The DHCPv6 server in ISC DHCP 4.0.x and 4.1.x before 4.1.2-P1, 4.0-ESV and 4.1-ESV before 4.1-ESV-R1, and 4.2.x before 4.2.1b1 allows remote attackers to cause a denial of service (assertion failure and daemon crash) by sending a message over IPv6 for a declined and abandoned address.
ISC DHCP server 4.0 before 4.0.2, 4.1 before 4.1.2, and 4.2 before 4.2.0-P1 allows remote attackers to cause a denial of service (NULL pointer dereference and crash) via a DHCPv6 packet containing a Relay-Forward message without an address in the Relay-Forward link-address field.
dhcpd in ISC DHCP 3.0.4 and 3.1.1, when the dhcp-client-identifier and hardware ethernet configuration settings are both used, allows remote attackers to cause a denial of service (daemon crash) via unspecified requests.