ntp - security update

Multiple vulnerabilities were discovered in ntp, an implementation of the
Network Time Protocol:

• CVE-2015-1798
  When configured to use a symmetric key with an NTP peer, ntpd would
  accept packets without MAC as if they had a valid MAC. This could
  allow a remote attacker to bypass the packet authentication and send
  malicious packets without having to know the symmetric key.
• CVE-2015-1799
  When peering with other NTP hosts using authenticated symmetric
  association, ntpd would update its internal state variables before
  the MAC of the NTP messages was validated. This could allow a remote
  attacker to cause a denial of service by impeding synchronization
  between NTP peers.

Additionally, it was discovered that generating MD5 keys using ntp-keygen
on big endian machines would either trigger an endless loop, or generate
non-random keys.

For the stable distribution (wheezy), these problems have been fixed in
version 1:4.2.6.p5+dfsg-2+deb7u4.

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

We recommend that you upgrade your ntp packages.