Network Time Protocol Vulnerabilities

OVERVIEW

Google Security Team researchers Neel Mehta and Stephen Roettger have coordinated multiple vulnerabilities with CERT/CC concerning the Network Time Protocol (NTP). As NTP is widely used within operational Industrial Control Systems deployments, NCCIC/ICS-CERT is providing this information for US Critical Infrastructure asset owners and operators for awareness and to identify mitigations for affected devices. ICS-CERT may release updates as additional information becomes available.
These vulnerabilities could be exploited remotely. Exploits that target these vulnerabilities are publicly available.
Products using NTP service prior to NTP-4.2.8 are affected. No specific vendor is specified because this is an open source protocol.

IMPACT

Exploitation of these vulnerabilities could allow an attacker to execute arbitrary code with the privileges of the ntpd process.

Impact to individual organizations depends on many factors that are unique to each organization. ICS-CERT recommends that organizations evaluate the impact of this vulnerability based on their operational environment, architecture, and product implementation.

BACKGROUND

The NTP is described in RFC 958a, an open source collaboration for acceptance and is used to synchronize system time over a network.

VULNERABILITY CHARACTERIZATION

VULNERABILITY OVERVIEW

INSUFFICIENT ENTROPYb

If the authentication key is not set in the configuration file, ntpd will generate a weak random key with insufficient entropy.

This vulnerability was resolved with NTP-dev4.2.7p11 on January 28, 2010.

CVE-2014-9293c has been assigned by CERT/CC to this vulnerability. A CVSS v2 base score of 7.3 has been assigned by CERT/CC; the CVSS vector string is (AV:N/AC:L/Au:M/C:P/I:P/A:C).d

USE OF CRYPTOGRAPHICALLY WEAK PRNGe

Prior to NTP-4.2.7p230 ntp-keygen used a weak seed to prepare a random number generator. The random numbers produced were then used to generate symmetric keys.
This vulnerability was resolved with NTP-dev4.2.7p230 on November 1, 2010.
CVE-2014-9294f has been assigned by CERT/CC to this vulnerability. A CVSS v2 base score of 7.3 has been assigned; the CVSS vector string is (AV:N/AC:L/Au:M/C:P/I:P/A:C).g

STACK-BASED BUFFER OVERFLOWSh

A remote attacker can send a carefully crafted packet that can overflow a stack buffer and potentially allow malicious code to be executed with the privilege level of the ntpd process. All NTP4 releases before 4.2.8 are vulnerable.
This vulnerability is resolved with NTP-stable4.2.8 on December 19, 2014.
CVE-2014-9295i has been assigned by CERT/CC to this vulnerability. A CVSS v2 base score of 7.3 has been assigned; the CVSS vector string is (AV:N/AC:L/Au:N/C:P/I:P/A:P).j

MISSING RETURN ON ERRORk

In the NTP code, a section of code is missing a return, and the resulting error indicates processing did not stop. This indicated a specific rare error occurred, which does not appear to affect system integrity. All NTP Version 4 releases before Version 4.2.8 are vulnerable.
This vulnerability is resolved with NTP-stable4.2.8 on December 19, 2014.
CVE-2014-9296l has been assigned by CERT/CC to this vulnerability. A CVSS v2 base score of 5.0 has been assigned; the CVSS vector string is (AV:N/AC:L/Au:N/C:N/I:N/A:P).m

VULNERABILITY DETAILS

EXPLOITABILITY

These vulnerabilities could be exploited remotely.

EXISTENCE OF EXPLOIT

Exploits that target these vulnerabilities are publicly available.

DIFFICULTY

An attacker with a low skill would be able to exploit these vulnerabilities.

MITIGATION

All NTP Version 4 releases, prior to Version 4.2.8, are vulnerable and need to be updated to Version 4.2.8.
ICS-CERT strongly encourages CIKR users to backup current operational ICS configurations, and thoroughly test the updated software for system compatibility on a test system before attempting deployment on operational systems.
CERT/CC has published a Vulnerability Note at the following URL:
http://www.kb.cert.org/vuls/id/852879
The latest NTP releases can be accessed at:
http://support.ntp.org/bin/view/Main/SoftwareDownloads.
ICS-CERT would like to thank NTP for coordinating with the Google Security Team Researchers.
ICS-CERT also encourages asset owners to take additional defensive measures to protect against this and other cybersecurity risks.

• Minimize network exposure for all control system devices and/or systems, and ensure that they are not accessible from the Internet.
• Locate control system networks and remote devices behind firewalls, and isolate them from the business network.
• When remote access is required, use secure methods, such as Virtual Private Networks (VPNs), recognizing that VPNs may have vulnerabilities and should be updated to the most current version available. Also recognize that VPN is only as secure as the connected devices.