Log Message:
Update isc-dhcp4 package to 4.2.3p2. (ISC DHCP 4.2.3-P2).
Alwo update isc-dhclient4, isc-dhcpd4 and isc-dhcrelay4.

			Changes since 4.2.3-P1

! Modify the DDNS handling code.  In a previous patch we added logging
  code to the DDNS handling.  This code included a bug that caused it
  to attempt to dereference a NULL pointer and eventually segfault.
  While reviewing the code as we addressed this problem, we determined
  that some of the updates to the lease structures would not work as
  planned since the structures being updated were in the process of
  being freed: these updates were removed.  In addition we removed an
  incorrect call to the DDNS removal function that could cause a failure
  during the removal of DDNS information from the DNS server.
  Thanks to Jasper Jongmans for reporting this issue.
  [ISC-Bugs #27078]
  CVE: CVE-2011-4868