ntp - security update

Several vulnerabilities were discovered in the Network Time Protocol
daemon and utility programs:

• CVE-2015-7974
  Matt Street discovered that insufficient key validation allows
  impersonation attacks between authenticated peers.
• CVE-2015-7977
  CVE-2015-7978
  Stephen Gray discovered that a NULL pointer dereference and a
  buffer overflow in the handling of ntpdc reslist commands may
  result in denial of service.
• CVE-2015-7979
  Aanchal Malhotra discovered that if NTP is configured for broadcast
  mode, an attacker can send malformed authentication packets which
  break associations with the server for other broadcast clients.
• CVE-2015-8138
  Matthew van Gundy and Jonathan Gardner discovered that missing
  validation of origin timestamps in ntpd clients may result in denial
  of service.
• CVE-2015-8158
  Jonathan Gardner discovered that missing input sanitising in ntpq
  may result in denial of service.
• CVE-2016-1547
  Stephen Gray and Matthew van Gundy discovered that incorrect handling
  of crypto NAK packets may result in denial of service.
• CVE-2016-1548
  Jonathan Gardner and Miroslav Lichvar discovered that ntpd clients
  could be forced to change from basic client/server mode to interleaved
  symmetric mode, preventing time synchronisation.
• CVE-2016-1550
  Matthew van Gundy, Stephen Gray and Loganaden Velvindron discovered
  that timing leaks in the packet authentication code could result
  in recovery of a message digest.
• CVE-2016-2516
  Yihan Lian discovered that duplicate IPs on unconfig directives will
  trigger an assert.
• CVE-2016-2518
  Yihan Lian discovered that an OOB memory access could potentially
  crash ntpd.

For the stable distribution (jessie), these problems have been fixed in
version 1:4.2.6.p5+dfsg-7+deb8u2.

For the testing distribution (stretch), these problems have been fixed
in version 1:4.2.8p7+dfsg-1.

For the unstable distribution (sid), these problems have been fixed in
version 1:4.2.8p7+dfsg-1.

We recommend that you upgrade your ntp packages.