CVE-2017-6464 in ntp
Summary
by MITRE
NTP before 4.2.8p10 and 4.3.x before 4.3.94 allows remote attackers to cause a denial of service (ntpd crash) via a malformed mode configuration directive.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 09/14/2020
The vulnerability identified as CVE-2017-6464 represents a critical denial of service flaw affecting the Network Time Protocol implementation in ntpd versions prior to 4.2.8p10 and 4.3.x versions before 4.3.94. This issue stems from inadequate input validation within the mode configuration directive parsing mechanism, creating a pathway for remote attackers to deliberately crash the ntpd daemon through carefully crafted malformed packets. The vulnerability specifically targets the configuration directive processing logic where the system fails to properly sanitize or validate the mode parameter values, leading to unpredictable behavior when handling malformed input. The flaw operates at the protocol level where ntpd receives and processes configuration directives from remote sources, making it particularly dangerous in networked environments where time synchronization services are critical.
The technical exploitation of this vulnerability occurs when an attacker sends a specially crafted packet containing a malformed mode configuration directive to a vulnerable ntpd instance. The daemon's parsing routine fails to handle the unexpected input gracefully, resulting in memory corruption or invalid pointer dereferences that ultimately cause the process to terminate abruptly. This type of vulnerability falls under the CWE-121 category of stack-based buffer overflow, though the specific implementation leads to a crash rather than arbitrary code execution. The attack vector is remote and requires no authentication, making it particularly dangerous in environments where ntpd is exposed to untrusted networks or where attackers can inject packets into time synchronization traffic flows.
The operational impact of CVE-2017-6464 extends beyond simple service disruption as it can compromise network time synchronization across entire infrastructure domains. When ntpd crashes repeatedly, it can cause cascading failures in systems that depend on accurate timekeeping for security operations, logging, and network coordination. This vulnerability aligns with ATT&CK technique T1499.004 for network denial of service attacks, where adversaries leverage protocol-level weaknesses to disrupt time synchronization services. The disruption can be particularly severe in environments using ntpd for critical infrastructure monitoring, where time synchronization is essential for security event correlation, certificate validation, and distributed system coordination. Organizations relying on ntpd for time services may experience extended periods of time synchronization failure, potentially leading to security incidents or compliance violations.
Mitigation strategies for this vulnerability require immediate patching of affected ntpd installations to versions 4.2.8p10 or 4.3.94 and later. Network administrators should implement firewall rules to restrict ntpd access to trusted sources only, reducing the attack surface for remote exploitation attempts. Additionally, monitoring systems should be configured to detect repeated ntpd crashes or restarts, which may indicate exploitation attempts. The vulnerability demonstrates the importance of input validation in network services and highlights the need for robust error handling in protocol implementations. Organizations should also consider implementing intrusion detection systems that can identify malformed ntp packets and automatically block suspicious traffic patterns. Regular security assessments of time synchronization infrastructure are essential to identify and remediate similar vulnerabilities before they can be exploited by adversaries.