dhcpcd before 5.2.12 allows remote attackers to execute arbitrary commands via shell metacharacters in a hostname obtained from a DHCP message.
The getoption function in dhcpcd 4.0.0 through 6.x before 6.4.3 allows remote DHCP servers to cause a denial of service by resetting the DHOOPTIONSOVERLOADED option in the (1) bootfile or (2) servername section, which triggers the option to be processed again.