NTP Bug 2918

TALOS-CAN-0062: Potential path traversal vulnerability in the config file saving of ntpd on VMS.

• Date Resolved: Stable (4.2.8p4) 21 Oct 2015
• References: Sec 2918 / CVE-2015-7851
• Affects: All ntp-4 releases running under VMS 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:N/I:P/A:C) Base Score: 5.2, worst case
• Summary: If ntpd is configured to allow remote configuration, and if the (possibly spoofed) IP address is allowed to send remote configuration requests, and if the attacker knows the remote configuration password or if ntpd was configured to disable authentication, then an attacker can send a set of packets to ntpd that may cause ntpd to overwrite files.
• 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 requires:
    • an explicitly configured "trusted" key. Only configure this if you need it.
    • access from permitted IP addresses. You choose the IPs.
    • authentication. Don't disable it. Practice key security safety.
  • Monitor your ntpd instances.
• Credit: This weakness was discovered by Yves Younan of Cisco Talos.