CVE-2017-6460 in ntp
Summary
by MITRE
Stack-based buffer overflow in the reslist function in ntpq in NTP before 4.2.8p10 and 4.3.x before 4.3.94 allows remote servers have unspecified impact via a long flagstr variable in a restriction list response.
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Analysis
by VulDB Data Team • 09/14/2020
The vulnerability identified as CVE-2017-6460 represents a critical stack-based buffer overflow affecting the Network Time Protocol implementation in ntpq utility. This flaw exists within the reslist function where improper handling of the flagstr variable during restriction list responses creates an exploitable condition that can be triggered remotely. The vulnerability affects NTP versions prior to 4.2.8p10 and 4.3.x versions prior to 4.3.94, indicating a significant window of affected releases that would have been widely deployed in production environments. The stack-based nature of this buffer overflow means that malicious actors can overwrite adjacent memory locations on the program stack, potentially leading to arbitrary code execution or service disruption.
The technical implementation of this vulnerability stems from insufficient bounds checking when processing the flagstr variable within restriction list responses. When remote servers send malformed restriction list data containing excessively long flagstr values, the ntpq utility fails to validate the input length before copying it into a fixed-size stack buffer. This classic buffer overflow condition allows attackers to overwrite return addresses, function pointers, and other critical stack data structures. The unspecified impact mentioned in the CVE description reflects the potential for various malicious outcomes including privilege escalation, denial of service, or remote code execution depending on the specific memory corruption patterns and target system configuration. This vulnerability directly maps to CWE-121 Stack-based Buffer Overflow, which is categorized under the broader weakness of insufficient input validation and memory safety issues in software development.
The operational impact of CVE-2017-6460 extends beyond simple exploitation as it affects time synchronization infrastructure that relies on NTP protocols across enterprise networks, cloud deployments, and critical infrastructure systems. Organizations using affected NTP versions face potential compromise of their time synchronization services, which can cascade into broader security issues including certificate validation failures, audit trail corruption, and authentication system instability. The remote nature of this vulnerability means that attackers need not be physically present within the network to exploit it, making it particularly dangerous for systems that communicate with external NTP servers. Attackers could leverage this vulnerability to gain unauthorized access to network time services or disrupt critical time-sensitive operations that depend on accurate time synchronization.
Mitigation strategies for CVE-2017-6460 should prioritize immediate patching of affected NTP installations to versions 4.2.8p10 or 4.3.94 and later. Organizations should also implement network segmentation and access controls to limit exposure of NTP services to untrusted networks, as recommended in the MITRE ATT&CK framework for network service exploitation techniques. Additional defensive measures include deploying intrusion detection systems capable of identifying malformed NTP restriction list responses and implementing strict input validation policies for time synchronization protocols. System administrators should conduct comprehensive vulnerability assessments to identify all affected systems and ensure that patches are applied across the entire network infrastructure. The vulnerability also highlights the importance of maintaining up-to-date security patches for time synchronization services and implementing regular security monitoring to detect potential exploitation attempts against critical infrastructure components.