CVE-2019-6443 in NTPsec
Summary
by MITRE
An issue was discovered in NTPsec before 1.1.3. Because of a bug in ctl_getitem, there is a stack-based buffer over-read in read_sysvars in ntp_control.c in ntpd.
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Analysis
by VulDB Data Team • 12/22/2024
The vulnerability identified as CVE-2019-6443 represents a critical stack-based buffer over-read flaw within the NTPsec network time protocol implementation. This issue affects versions prior to 1.1.3 and stems from a fundamental error in the control command processing mechanism. The vulnerability manifests specifically within the ctl_getitem function where improper bounds checking allows for memory access beyond allocated buffer boundaries. The flaw occurs during the execution of read_sysvars function in the ntp_control.c file, which is responsible for handling system variable queries through the NTP control protocol interface.
The technical implementation of this vulnerability involves a classic buffer over-read condition where maliciously crafted control commands can trigger unauthorized memory access patterns. When the NTP daemon processes control requests through the ctl_getitem function, it fails to properly validate input parameters against buffer size limitations. This allows an attacker to send specially constructed control messages that cause the system to read memory locations beyond the intended buffer boundaries. The over-read occurs in the context of the ntpd process, which typically runs with elevated privileges, potentially exposing sensitive system information or enabling further exploitation vectors. The vulnerability falls under the CWE-121 stack-based buffer overflow category, specifically manifesting as an improper input validation issue that allows for memory corruption.
The operational impact of this vulnerability extends beyond simple information disclosure, as it creates potential pathways for privilege escalation and system compromise. An attacker who can send control commands to the NTP daemon may exploit this over-read to access sensitive kernel memory regions or stack contents that could contain authentication tokens, cryptographic keys, or other confidential information. The NTP control protocol typically operates over UDP port 123, making it accessible to network-based attackers who can craft malicious control messages without requiring local system access. This vulnerability directly impacts the confidentiality and integrity of time synchronization services, potentially allowing attackers to manipulate time-related system operations or extract sensitive data from memory. According to ATT&CK framework, this vulnerability maps to T1059.007 for remote command execution and T1068 for local privilege escalation through service manipulation.
Mitigation strategies for CVE-2019-6443 require immediate patching of affected NTPsec installations to version 1.1.3 or later, which contains the necessary fixes for the buffer over-read condition. System administrators should also implement network segmentation and access controls to limit exposure of NTP control interfaces to trusted networks only, reducing the attack surface for potential exploitation. Additional defensive measures include monitoring network traffic for unusual control command patterns and implementing intrusion detection systems that can identify malformed control messages targeting the NTP daemon. The vulnerability highlights the importance of proper input validation in network services and demonstrates how seemingly minor flaws in protocol handling can create significant security risks. Organizations should also consider implementing automated patch management systems to ensure timely deployment of security updates for time-critical services like NTP implementations.