Univention Corporate Server 4.3 erratum 380 (security)

This update addresses the following issues:
* exif: buffer over-read in exif_process_IFD_in_MAKERNOTE() (CVE-2018-14851)
* exif: integer overflow leading to out-of-bound buffer read in
  exif_thumbnail_extract() (CVE-2018-14883)
* Cross-site scripting (XSS) flaw in Apache2 component via body of
  'Transfer-Encoding: chunked' request (CVE-2018-17082)
* imap_open() allows running arbitrary shell commands via mailbox parameter
  (CVE-2018-19518)
* ext/imap/php_imap.c allows remote attackers to cause a denial of service
  (NULL pointer dereference and application crash) via an empty string in the
  message argument to the imap_mail function. (CVE-2018-19935)