The Network Time Protocol (NTP) provides networked systems and devices with a way to synchronize time for various services and applications. The reference implementation produced by the NTP Project (ntp.org) contains several vulnerabilities.

CWE-290: Authentication Bypass by Spoofing - CVE-2014-9298

The IPv6 address ::1 can be spoofed, allowing an attacker to bypass ACLs based on ::1.

CWE-754: Improper Check for Unusual or Exceptional Conditions - CVE-2014-9297

The length value in extension field pointers is not properly validated, allowing information leaks.

CWE-332: Insufficient Entropy in PRNG - CVE-2014-9293

If no authentication key is defined in the ntp.conf file, a cryptographically-weak default key is generated.

CWE-338: Use of Cryptographically Weak Pseudo-Random Number Generator (PRNG) - CVE-2014-9294

ntp-keygen before 4.2.7p230 uses a non-cryptographic random number generator with a weak seed to generate symmetric keys.

CWE-121: Stack Buffer Overflow - CVE-2014-9295

A remote unauthenticated attacker may craft special packets that trigger buffer overflows in the ntpd functions crypto_recv() (when using autokey authentication), ctl_putdata(), and configure(). The resulting buffer overflows may be exploited to allow arbitrary malicious code to be executed with the privilege of the ntpd process.

CWE-389: Error Conditions, Return Values, Status Codes - CVE-2014-9296

A section of code in ntpd handling a rare error is missing a return statement, therefore processing did not stop when the error was encountered. This situation may be exploitable by an attacker.

The NTP Project provides more information about these issues in their security advisory.

The NTP Project implementation is widely used in operating system distributions and network products. These vulnerabilities affect ntpd acting as a server or client. CERT/CC is not aware of any public exploit of these vulnerabilities at this time.

The CVSS score below is based on the buffer overflow vulnerabilities (CVE-2014-9295).

The buffer overflow vulnerabilities in ntpd may allow a remote unauthenticated attacker to execute arbitrary malicious code with the privilege level of the ntpd process. The weak default key and non-cryptographic random number generator in ntp-keygen may allow an attacker to gain information regarding the integrity checking and authentication encryption schemes. More specifically, the weak default key allows access to private mode and control mode queries that require authentication, if not restricted by the configuration.

Apply an update

These issues have been addressed in ntp-4.2.8p1. The update may be downloaded from ntp.org.

Restrict status queries

As noted in the announcement for ntp-4.2.8:

The vulnerabilities listed below can be significantly mitigated by following the BCP of putting


restrict default ... noquery

in the ntp.conf file.  With the exception of:

  receive(): missing return on error
  References: Sec 2670 / CVE-2014-9296 / VU#852879

below (which is a limited-risk vulnerability), none of the recent vulnerabilities listed below can be exploited if the source IP is restricted from sending a 'query'-class packet by your ntp.conf file.

Use firewall rules

Install firewall rules that block ::1 IPv6 address from inappropriate network interfaces.

Disable autokey authentication

Disable Autokey Authentication by removing, or commenting out, all configuration directives beginning with the crypto keyword in your ntp.conf file.