Univention Corporate Server 4.4 erratum 49 (security)

This update addresses the following issues:
* Integer overflow in transport read resulting in out of bounds write
  (CVE-2019-3855)
* Integer overflow in keyboard interactive handling resulting in out of
  bounds write (CVE-2019-3856)
* Integer overflow in SSH packet processing channel resulting in out of
  bounds write (CVE-2019-3857)
* Zero-byte allocation with a specially crafted SFTP packed leading to an
  out-of-bounds read (CVE-2019-3858)
* Unchecked use of _libssh2_packet_require and _libssh2_packet_requirev
  resulting in out-of-bounds read (CVE-2019-3859)
* Out-of-bounds reads with specially crafted SFTP packets (CVE-2019-3860)
* Out-of-bounds reads with specially crafted SSH packets (CVE-2019-3861)
* Out-of-bounds memory comparison with specially crafted message channel
  request (CVE-2019-3862)
* Integer overflow in user authenticate keyboard interactive allows
  out-of-bounds writes (CVE-2019-3863)