Univention Corporate Server 4.2 erratum 210 (security)

This update addresses the following issue(s):
* In res/res_rtp_asterisk.c unauthorized data disclosure (media takeover
  in the RTP stack) is possible with careful timing by an attacker. The
  "strictrtp" option in rtp.conf enables a feature of the RTP stack that
  learns the source address of media for a session and drops any packets
  that do not originate from the expected address. This option is enabled
  by default in Asterisk 11 and above. The "nat" and "rtp_symmetric"
  options (for chan_sip and chan_pjsip, respectively) enable symmetric RTP
  support in the RTP stack. This uses the source address of incoming media
  as the target address of any sent media. This option is not enabled by
  default, but is commonly enabled to handle devices behind NAT. A change
  was made to the strict RTP support in the RTP stack to better tolerate
  late media when a reinvite occurs. When combined with the symmetric RTP
  support, this introduced an avenue where media could be hijacked. Instead
  of only learning a new address when expected, the new code allowed a new
  source address to be learned at all times. If a flood of RTP traffic was
  received, the strict RTP support would allow the new address to provide
  media, and (with symmetric RTP enabled) outgoing traffic would be sent to
  this new address, allowing the media to be hijacked. Provided the attacker
  continued to send traffic, they would continue to receive traffic as well.
  (CVE-2017-14099)
* Unauthorized command execution is possible. The app_minivm module has an
  "externnotify" program configuration option that is executed by the
  MinivmNotify dialplan application. The application uses the caller-id
  name and number as part of a built string passed to the OS shell for
  interpretation and execution. Since the caller-id name and number can
  come from an untrusted source, a crafted caller-id name or number allows
  an arbitrary shell command injection. (CVE-2017-14100)
* insufficient RTCP packet validation could allow reading stale buffer
  contents and when combined with the "nat" and "symmetric_rtp" options
  allow redirecting where Asterisk sends the next RTCP report
  (CVE-2017-14603)