NTP Bug 2921

TALOS-CAN-0065: Password Length Memory Corruption Vulnerability

• Date Resolved: Stable (4.2.8p4) 21 Oct 2015
• References: Sec 2921 / CVE-2015-7854
• Affects: All ntp-4 releases up to, but not including 4.2.8p4, and 4.3.0 up to, but not including 4.3.77
• CVSS: (AV:N/AC:H/Au:M/C:C/I:C/A:C) Base Score: 0.0 best case, 1.7 usual case, 6.8, worst case
• Summary: If ntpd is configured to allow remote configuration, and if the (possibly spoofed) source IP address is allowed to send remote configuration requests, and if the attacker knows the remote configuration password or if ntpd was (foolishly) configured to disable authentication, then an attacker can send a set of packets to ntpd that may cause it to crash, with the hypothetical possibility of a small code injection.
• Mitigation:
  • Implement BCP-38.
  • Upgrade to 4.2.8p4, or later, from the NTP Project Download Page or the NTP Public Services Project Download Page.
  • If you are unable to upgrade, remote configuration of NTF's ntpd equires:
    • an explicitly configured "trusted" key. Only configure this if you need it.
    • access from a permitted IP address. You choose the IPs.
    • authentication. Don't disable it. Practice secure key safety.
  • Monitor your ntpd instances.
• Credit: This weakness was discovered by Yves Younan and Aleksander Nikolich of Cisco Talos.