A new version of the Network Time Protocol daemon (ntpd) released last week by the NTP Project addresses several vulnerabilities, including a high severity issue introduced by a previous patch.
Ntp-4.2.8p8 resolves a total of five vulnerabilities. The most serious of them is CVE-2016-4957, a high severity denial-of-service (DoS) flaw that can be exploited to cause ntpd to crash.
The security hole was introduced by the fix for CVE-2016-1547, an issue patched in April after it was reported by Stephen Gray and Matthew Van Gundy of Cisco ASIG. CVE-2016-1547 is related to the processing of crypto NAK packets and it can be exploited by an off-path attacker to cause a preemptable client association to be demobilized.
The other vulnerabilities, reported to the NTP Project by Miroslav Lichvar and Jakub Prokes of Red Hat, have been rated as having low severity. They have been described as bad authentication demobilizes ephemeral associations (CVE-2016-4953), processing spoofed server packets (CVE-2016-4954), autokey association reset (CVE-2016-4955), and a broadcast interleave issue (CVE-2016-4956). CVE-2016-4956 is caused by an incomplete fix for a previously discovered flaw.
An advisory published by US-CERT shows that the products of many major vendors could be affected by these NTP vulnerabilities.
Red Hat has clarified that Red Hat Enterprise Linux is not affected by CVE-2016-4957 as the fix developed by the company for CVE-2016-1547 is different from the upstream patch.
Cisco has also published an advisory to inform customers that it’s currently trying to determine which of its products are affected by the NTP flaws. So far, the company has confirmed that one or more of these bugs affect some of its collaboration and social media, endpoint client, hosted services, network and content security, network management and provisioning, and network application, service and acceleration products.
Researchers from Chinese security firm Qihoo 360 warned at the Hack in the Box (HITB) conference last month that remote attackers can wirelessly change the time on NTP servers over long distances using widely available, inexpensive devices.