ntpd in NTP 4.2.8p3 and NTPsec a5fb34b9cc89b92a8fef2f459004865c93bb7f92 relies on the underlying operating system to protect it from requests that impersonate reference clocks. Because reference clocks are treated like other peers and stored in the same structure, any packet with a source ip address of a reference clock (127.127.1.1 for example) that reaches the receive() function will match that reference clock's peer record and will be treated as a trusted peer. Any system that lacks the typical martian packet filtering which would block these packets is in danger of having its time controlled by an attacker.
The MITRE CVE dictionary describes this issue as:
Find out more about CVE-2016-1551 from the MITRE CVE dictionary dictionary and NIST NVD.
This issue did not affect the versions of ntp as shipped with Red Hat Enterprise Linux 5, 6, and 7 as the Linux kernel drops packets from 127.0.0.0/8, mitigating this issue.
NOTE: The following CVSS v2 metrics and score provided are preliminary and subject to review.
| Base Score | 2.6 |
|---|---|
| Base Metrics | AV:N/AC:H/Au:N/C:N/I:P/A:N |
| Access Vector | Network |
| Access Complexity | High |
| Authentication | None |
| Confidentiality Impact | None |
| Integrity Impact | Partial |
| Availability Impact | None |
Find out more about Red Hat support for the Common Vulnerability Scoring System (CVSS).
| Platform | Package | State |
|---|---|---|
| Red Hat Enterprise Linux 7 | ntp | Not affected |
| Red Hat Enterprise Linux 6 | ntp | Not affected |
| Red Hat Enterprise Linux 5 | ntp | Not affected |
Vulmon