NTP users are strongly urged to take immediate action to ensure that their NTP daemons are not susceptible to being used in distributed denial-of-service (DDoS) attacks. Please also take this opportunity to defeat denial-of-service attacks by implementing Ingress and Egress filtering through BCP38.

ntp-4.2.8p10 was released on 21 March 2017. It addresses 6 medium- and 5 low-severity security issues, 4 informational security topics, 15 bugfixes, and contains other improvements over 4.2.8p9.

Please see the NTP Security Notice for vulnerability and mitigation details.

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Are you using Autokey in production? If so, please contact Harlan - he's got some questions for you.

NTP Bug 3378

NTP-01-003 NTP: Improper use of snprintf() in mx4200_send() (Low)

• Date Resolved: 21 Mar 2017
• References: Sec 3378 / CVE-2017-6451 / VU#325339
• Affects: All versions of NTP, up to but not including ntp-4.2.8p10, and ntp-4.3.0 up to, but not including ntp-4.3.94.
• CVSS2: LOW 0.8 (AV:L/AC:H/Au:M/C:N/I:N/A:P)
• CVSS3: LOW 1.8 CVSS:3.0/AV:L/AC:H/PR:H/UI:R/S:U/C:N/I:L/A:N
• Summary: The legacy MX4200 refclock is only built if is specifically enabled, and furthermore additional code changes are required to compile and use it. But it uses the libc function snprintf()/vsnprintf() incorrectly, which can lead to an out-of-bounds memory write due to an improper handling of the return value of snprintf()/vsnprintf(). Since the return value is used as an iterator and it can be larger than the buffer’s size, it is possible for the iterator to point somewhere outside of the allocated buffer space. This results in an out-of-bound memory write. This behavior can be leveraged to overwrite a saved instruction pointer on the stack and gain control over the execution flow. During testing it was not possible to identify any malicious usage for this vulnerability. Specifically, no way for an attacker to exploit this vulnerability was ultimately unveiled. However, it has the potential to be exploited, so the code should be fixed.
• Mitigation, if you have a Magnavox MX4200 refclock:
  • Upgrade to 4.2.8p10, or later, from the NTP Project Download Page or the NTP Public Services Project Download Page.
  • Properly monitor your ntpd instances, and auto-restart ntpd (without -g) if it stops running.
• Credit: This weakness was discovered by Cure53.