Univention Corporate Server 4.2 erratum 275 (security)

This update addresses the following issues:
* FR-GV-205 issue allows "DHCP - Buffer over-read in
  fr_dhcp_decode_options()" and a denial of service. (CVE-2017-10982)
* FR-GV-206 issue allows "DHCP - Read overflow when decoding option 63" and a
  denial of service. (CVE-2017-10983)
* FR-GV-203 issue allows "DHCP - Memory leak in decode_tlv()" and a denial of
  service. (CVE-2017-10980)
* FR-GV-202 issue allows "Write overflow in rad_coalesce()" - this allows
  remote attackers to cause a denial of service (daemon crash) or possibly
  execute arbitrary code. (CVE-2017-10979)
* FR-GV-204 issue allows "DHCP - Memory leak in fr_dhcp_decode()" and a
  denial of service. (CVE-2017-10981)
* FR-GV-201 issue allows "Read / write overflow in make_secret()" and a
  denial of service. (CVE-2017-10978)