CVE-2015-5194 in ntpd
Summary
by MITRE
The log_config_command function in ntp_parser.y in ntpd in NTP before 4.2.7p42 allows remote attackers to cause a denial of service (ntpd crash) via crafted logconfig commands.
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Analysis
by VulDB Data Team • 06/25/2022
The vulnerability identified as CVE-2015-5194 represents a critical denial of service flaw within the Network Time Protocol daemon implementation. This issue resides in the log_config_command function located within the ntp_parser.y file of ntpd, which is part of the NTP software suite prior to version 4.2.7p42. The vulnerability enables remote attackers to trigger a crash of the ntpd process through the deliberate crafting of malformed logconfig commands, effectively disrupting time synchronization services across affected systems. The flaw demonstrates a classic buffer over-read condition that occurs when the parser fails to properly validate input parameters before processing them.
From a technical perspective, this vulnerability operates through improper input validation mechanisms within the NTP parser component. When ntpd receives crafted logconfig commands, the log_config_command function processes these inputs without adequate bounds checking or sanitization. The function fails to properly handle malformed or excessively long command parameters, leading to memory corruption that ultimately results in process termination. This behavior aligns with CWE-129, which describes improper validation of length of inputs, and represents a specific instance of CWE-125, indicating an out-of-bounds read condition. The vulnerability exists at the parsing layer where user-supplied data transitions from network input to internal processing, creating an attack surface that remote adversaries can exploit without requiring authentication or elevated privileges.
The operational impact of CVE-2015-5194 extends beyond simple service disruption to potentially compromise time synchronization infrastructure across affected networks. When exploited, the vulnerability causes ntpd to crash and restart, creating temporary gaps in time services that can affect system logging, authentication mechanisms, and network coordination protocols that depend on accurate timekeeping. This is particularly concerning in enterprise environments where precise time synchronization is critical for security auditing, compliance requirements, and distributed system coordination. The vulnerability affects systems that process external NTP commands, making it applicable to any network environment where NTP servers accept configuration commands from remote sources, including internet-facing time servers and internal network infrastructure components.
Mitigation strategies for CVE-2015-5194 primarily focus on immediate software updates and operational hardening measures. The most effective solution involves upgrading to NTP version 4.2.7p42 or later, which includes patches specifically addressing the input validation issues within the log_config_command function. Organizations should also implement network segmentation to limit exposure of NTP servers to untrusted networks and consider disabling unnecessary NTP configuration command processing capabilities. From a defensive standpoint, this vulnerability aligns with ATT&CK technique T1499.001, which describes network disruption attacks, and represents a form of service denial that can be classified under the broader category of availability attacks. System administrators should monitor for exploitation attempts through network traffic analysis and implement proper logging to detect malformed NTP commands that may indicate attempted exploitation of this vulnerability.