CVE-2016-9310 in ntpd
Summary
by MITRE
The control mode (mode 6) functionality in ntpd in NTP before 4.2.8p9 allows remote attackers to set or unset traps via a crafted control mode packet.
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Analysis
by VulDB Data Team • 05/13/2026
The vulnerability identified as CVE-2016-9310 affects the Network Time Protocol daemon (ntpd) version 4.2.8p8 and earlier, representing a critical security flaw in the control mode packet handling mechanism. This vulnerability specifically targets mode 6 functionality within ntpd, which is designed to provide administrative control over the NTP daemon through control mode packets. The issue stems from insufficient input validation and sanitization of control mode packets, allowing remote attackers to manipulate the system's trap settings without proper authentication or authorization. The control mode in NTP is intended for legitimate administrative purposes, including configuration changes, monitoring, and system diagnostics, but this vulnerability enables unauthorized manipulation of these control mechanisms.
The technical exploitation of this vulnerability occurs through the manipulation of control mode packets sent to the ntpd daemon, specifically targeting mode 6 packets that are meant to carry administrative commands. Attackers can craft malicious control mode packets that contain specially formatted data to either set or unset system traps, which are typically used for logging or alerting purposes within the NTP daemon. This flaw essentially allows an attacker to modify the daemon's operational behavior by altering trap configurations, potentially enabling them to disable security logging mechanisms or redirect system alerts to unauthorized parties. The vulnerability resides in the packet parsing logic where ntpd fails to properly validate the contents of control mode packets before executing the commands they contain, creating a path for privilege escalation through unauthorized administrative control.
The operational impact of this vulnerability extends beyond simple administrative manipulation, as it can significantly compromise the integrity and security posture of time synchronization services within network infrastructure. When an attacker successfully exploits this vulnerability, they can potentially disable critical logging mechanisms that would normally alert administrators to suspicious activities or system misconfigurations. This capability undermines the fundamental security model of NTP implementations, where control mode functionality is expected to be restricted to authenticated administrators. The vulnerability is particularly concerning in enterprise environments where NTP servers serve as critical infrastructure components for maintaining time synchronization across multiple systems, as it could enable attackers to disrupt time services or create false log entries that mask other security incidents. The lack of proper access controls for mode 6 functionality means that any remote attacker with network access to the NTP daemon can potentially exploit this flaw, making it a high-risk vulnerability for networked systems.
Organizations should implement immediate mitigations including updating to NTP version 4.2.8p9 or later, which contains the necessary patches to address the control mode packet validation issues. Network segmentation and firewall rules should be implemented to restrict access to NTP ports to trusted administrative networks only, limiting the attack surface for this vulnerability. The implementation of network monitoring solutions that can detect anomalous control mode packet traffic patterns may help identify potential exploitation attempts. Additionally, organizations should conduct thorough security assessments of their NTP configurations to ensure that unnecessary administrative access is not granted to untrusted networks. From a compliance perspective, this vulnerability aligns with CWE-20, which describes improper input validation, and could be mapped to ATT&CK technique T1072 for software deployment tools, as it involves manipulation of system control mechanisms through network-based attacks. The vulnerability also represents a significant concern for organizations following NIST SP 800-53 security controls, particularly those related to system and information integrity, as it compromises the integrity of time synchronization services and the logging mechanisms that support security monitoring.