Univention Corporate Server 4.2 erratum 441 (security)

This update addresses the following issues:
* Path traversal via crafted tar file containing symlink (CVE-2011-5325)
* unprivileged arbitrary module load via basename abuse (CVE-2014-9645)
* Segmentation fault when unzipping specially crafted zip file
  (CVE-2015-9261)
* out of bounds write (heap) due to integer underflow in udhcpc
  (CVE-2016-2147)
* heap-based buffer overflow in OPTION_6RD parsing (CVE-2016-2148)
* Integer overflow in the get_next_block function (CVE-2017-15873)
* Insufficient sanitization of filenames when autocompleting (CVE-2017-16544)
* wget: Heap-based buffer overflow in the retrieve_file_data() function
  (CVE-2018-1000517)