Univention Corporate Server 4.3 erratum 648 (extended maintenance)

This update addresses the following issues:
* PHP DirectoryIterator class accepts filenames with embedded \0 byte and
  treats them as terminating at that byte (CVE-2019-11045)
* Out-of-bounds read in bc_shift_addsub (CVE-2019-11046)
* Information disclosure in exif_read_data() (CVE-2019-11047)
* Out-of-bounds read when parsing EXIF information (CVE-2019-11050)
* Out of bounds read in php_strip_tags_ex (CVE-2020-7059)
* Global buffer-overflow in mbfl_filt_conv_big5_wchar function
  (CVE-2020-7060)