CVE-2015-7703 in ntpd
Summary
by MITRE
The "pidfile" or "driftfile" directives in NTP ntpd 4.2.x before 4.2.8p4, and 4.3.x before 4.3.77, when ntpd is configured to allow remote configuration, allows remote attackers with an IP address that is allowed to send configuration requests, and with knowledge of the remote configuration password to write to arbitrary files via the :config command.
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Analysis
by VulDB Data Team • 06/25/2022
The vulnerability identified as CVE-2015-7703 represents a critical configuration flaw in the Network Time Protocol daemon ntpd that affects versions prior to 4.2.8p4 and 4.3.77. This weakness specifically targets the pidfile and driftfile directives within the NTP configuration system, creating a path for remote attackers to execute arbitrary file write operations through the configuration interface. The vulnerability operates under the premise that an attacker must possess both network access to the NTP server and knowledge of the configuration password, which together provide the necessary credentials to exploit the system. The flaw stems from insufficient input validation and sanitization of configuration commands, particularly the :config command that processes user-provided file paths without adequate verification of their legitimacy or safety. This vulnerability is classified under CWE-22, which deals with Improper Limitation of a Pathname to a Restricted Directory, and falls within the broader category of path traversal and file manipulation vulnerabilities that have historically plagued network services.
The operational impact of CVE-2015-7703 extends beyond simple unauthorized file access, as it enables attackers to potentially overwrite critical system files, inject malicious code into the NTP daemon, or manipulate time synchronization settings across the network. When combined with the ATT&CK technique T1059.007 for Command and Scripting Interpreter, this vulnerability allows attackers to escalate privileges and maintain persistent access through the NTP service. The attack vector requires that the NTP server be configured to accept remote configuration requests, which is a common practice in enterprise environments where centralized time management is essential. However, this configuration opens the door to exploitation by attackers who can leverage the configuration password to send crafted :config commands that write to arbitrary file locations. The implications are particularly severe in environments where NTP is used for critical infrastructure time synchronization, as attackers could manipulate time settings to disrupt services, bypass security controls, or create backdoors for future access. The vulnerability's presence in widely deployed NTP versions means that numerous organizations across various industries were potentially exposed to this risk, making it a significant concern for network security teams managing time synchronization services.
Mitigation strategies for CVE-2015-7703 must address both the immediate configuration issues and broader security practices surrounding NTP service management. Organizations should immediately upgrade to NTP versions 4.2.8p4 or later, or 4.3.77 and newer, which contain patches specifically designed to prevent arbitrary file write operations through the configuration interface. The recommended approach involves disabling remote configuration capabilities when possible, as this eliminates the attack surface entirely for this particular vulnerability. Security teams should implement strict access controls for the NTP configuration interface, ensuring that only authorized personnel can submit configuration commands and that configuration passwords are properly secured and rotated. Network segmentation should be employed to limit access to NTP services to only necessary systems, reducing the potential impact of exploitation. Additionally, monitoring and logging should be enhanced to detect unusual configuration changes or file write operations that could indicate exploitation attempts. The vulnerability serves as a reminder of the importance of proper input validation and privilege separation in network services, particularly those that handle configuration changes. Organizations should also consider implementing network-based intrusion detection systems that can identify and alert on suspicious NTP configuration commands, providing an additional layer of defense against this and similar vulnerabilities. Regular security audits of NTP configurations should be conducted to ensure that remote configuration capabilities are properly secured and that access controls remain effective against evolving threats.