CVE-2016-2519 in ntp
Summary
by MITRE
ntpd in NTP before 4.2.8p7 and 4.3.x before 4.3.92 allows remote attackers to cause a denial of service (ntpd abort) by a large request data value, which triggers the ctl_getitem function to return a NULL value.
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Analysis
by VulDB Data Team • 07/27/2022
The vulnerability identified as CVE-2016-2519 represents a critical denial of service weakness in the Network Time Protocol daemon implementation across multiple versions of the NTP software ecosystem. This flaw affects ntpd versions prior to 4.2.8p7 and 4.3.x versions prior to 4.3.92, creating a persistent security risk for network infrastructure relying on time synchronization services. The vulnerability stems from improper input validation within the control message processing mechanism of the NTP daemon, specifically within the ctl_getitem function that handles requests for system information and configuration parameters.
The technical exploitation of this vulnerability occurs when a remote attacker crafts a malicious NTP control message containing an excessively large request data value. This malformed request triggers the ctl_getitem function to return a NULL pointer value instead of proper response data, causing the ntpd process to terminate abruptly through an abort condition. The flaw demonstrates characteristics consistent with CWE-476_NULL_Pointer_Dereference, where the application fails to properly handle NULL return values from function calls, leading to unexpected program termination. The vulnerability operates at the application layer of the network stack, leveraging the NTP control message protocol to deliver the malicious payload without requiring authentication or privileged access.
The operational impact of CVE-2016-2519 extends beyond simple service disruption to potentially compromise network time synchronization across entire infrastructure domains. When exploited, the vulnerability can cause cascading failures in time-sensitive applications, network monitoring systems, and distributed services that depend on accurate timekeeping. The denial of service condition affects the availability of time synchronization services, which can lead to authentication failures, log timestamp inconsistencies, and broader network operational degradation. This vulnerability aligns with ATT&CK technique T1499.004 for Network Denial of Service, specifically targeting the availability aspect of network services through process termination attacks.
Mitigation strategies for CVE-2016-2519 require immediate deployment of patched NTP daemon versions, with the recommended upgrade path to NTP 4.2.8p7 or 4.3.92 and subsequent releases. Network administrators should implement firewall rules to restrict NTP control message access to trusted management systems only, reducing the attack surface for remote exploitation. Additionally, monitoring systems should be configured to detect unusual ntpd process termination patterns and abnormal control message traffic. The vulnerability highlights the importance of robust input validation and proper error handling in network services, emphasizing the need for defensive programming practices that prevent NULL pointer dereferences. Organizations should also consider implementing intrusion detection systems capable of identifying malformed NTP control messages and establishing incident response procedures for rapid remediation of time synchronization service disruptions.