Univention Corporate Server 4.3 erratum 492 (security)

This update addresses the following issues:
* Invalid memory access in the zzip_disk_fread function in zzip/mmapped.c
  (CVE-2018-6381)
* Loading of misaligned memory address in zip.c:__zzip_fetch_disk_trailer can
  lead to a denial of service via crafted zip file (CVE-2018-6484)
* Bus error in zzip_disk_findfirst function in zzip/mmapped.c (CVE-2018-6540)
* Bus error caused by loading of a misaligned address inzzip/zip.c
  (CVE-2018-6541)
* Uncontrolled memory allocation in __zzip_parse_root_directory in zzip/zip.c
  (CVE-2018-6869)
* Out of bound read in mmapped.c:zzip_disk_fread() causes crash
  (CVE-2018-7725)
* Bus error in zip.c:__zzip_parse_root_directory() cause crash via crafted
  zip file (CVE-2018-7726)
* Memory leak triggered in the function __zzip_parse_root_directory in zip.c
  (CVE-2018-16548)