ISC dhclient vulnerability

"The ISC dhclient contains a vulnerability that could allow a remote
attacker to execute arbitrary code on the client machine.

This vulnerability is addressed in ISC DHCP version 3.1-ESV-R1,
4.1-ESV-R2 and 4.2.1-P1. Users of ISC DHCP from the original source
distribution should upgrade to this version or later, as appropriate.
Users who obtain ISC DHCP from a third-party vendor, such as their
operating system vendor, should see the vendor information portion of
this document for a partial list of affected vendors."