CVE-2017-6463 in ntp
Summary
by MITRE
NTP before 4.2.8p10 and 4.3.x before 4.3.94 allows remote authenticated users to cause a denial of service (daemon crash) via an invalid setting in a :config directive, related to the unpeer option.
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Analysis
by VulDB Data Team • 09/14/2020
The vulnerability identified as CVE-2017-6463 represents a critical denial of service flaw affecting the Network Time Protocol daemon across multiple versions of the ntpd software. This issue specifically targets ntpd versions prior to 4.2.8p10 and 4.3.x versions prior to 4.3.94, creating a significant risk for network infrastructure relying on time synchronization services. The vulnerability stems from inadequate input validation within the configuration processing mechanism, particularly when handling the :config directive with malformed unpeer option settings.
The technical exploitation of this vulnerability occurs through a carefully crafted configuration directive that includes an invalid setting within the :config directive. When the ntpd daemon processes such malformed input, it fails to properly validate the unpeer option parameter, leading to a critical failure in the daemon's memory management and control flow. This improper handling results in an abrupt daemon crash, effectively rendering the time synchronization service unavailable to network clients. The flaw is classified as a remote authenticated vulnerability, meaning that an attacker with valid credentials to access the ntpd configuration interface can trigger the denial of service condition without requiring physical access or elevated privileges beyond authentication.
From an operational perspective, this vulnerability poses substantial risk to network infrastructure stability and availability. Organizations relying on ntpd for time synchronization across critical systems face potential disruptions to their network operations, as the daemon crash would interrupt time services for all connected devices. The impact extends beyond simple service interruption, as many network protocols and security systems depend on synchronized time for proper operation, including authentication mechanisms, logging, and cryptographic operations. This vulnerability particularly affects enterprise networks where time synchronization is crucial for maintaining security posture and operational continuity.
The vulnerability aligns with CWE-121, which addresses stack-based buffer overflow conditions, and demonstrates characteristics consistent with improper input validation patterns found in the MITRE ATT&CK framework under the T1499 category for network denial of service. The flaw represents a classic case of insufficient validation of configuration inputs, where the ntpd daemon fails to implement proper sanitization and validation routines for user-supplied parameters within the :config directive. Organizations should immediately implement mitigation strategies including updating to patched versions of ntpd, implementing network segmentation to limit access to configuration interfaces, and deploying monitoring solutions to detect potential exploitation attempts. Additionally, administrators should review and restrict authentication access to ntpd configuration interfaces, as the vulnerability requires authenticated access to execute successfully, making access control a critical defensive measure.