CVE-2019-6445 in NTPsec
Summary
by MITRE
An issue was discovered in NTPsec before 1.1.3. An authenticated attacker can cause a NULL pointer dereference and ntpd crash in ntp_control.c, related to ctl_getitem.
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Analysis
by VulDB Data Team • 12/22/2024
The vulnerability identified as CVE-2019-6445 represents a critical denial of service weakness within the NTPsec network time protocol implementation. This flaw exists in versions prior to 1.1.3 and specifically targets the ntp_control.c module where the ctl_getitem function processes control requests. The issue manifests as a NULL pointer dereference that occurs when an authenticated attacker submits malicious control commands to the ntpd daemon. This type of vulnerability falls under the category of improper handling of null values as defined by CWE-476, which is classified as a null pointer dereference condition that can lead to application crashes and system instability.
The technical exploitation of this vulnerability requires an authenticated attacker who possesses valid credentials to communicate with the NTP daemon. When the ctl_getitem function processes certain control commands, it fails to properly validate input parameters before attempting to dereference pointers that may be NULL. This occurs during the control message processing phase where the daemon handles requests for system information and configuration parameters. The flaw is particularly concerning because it can be triggered through legitimate control interfaces, making it difficult to distinguish between malicious and legitimate traffic at the network level. The vulnerability directly impacts the availability of time synchronization services since the ntpd process terminates upon encountering the NULL pointer dereference, effectively removing the system from the network time synchronization infrastructure.
The operational impact of CVE-2019-6445 extends beyond simple service disruption as it can compromise the reliability of time-critical systems that depend on NTPsec for accurate timekeeping. Organizations utilizing NTPsec for network infrastructure time synchronization, financial transactions, security logging, and distributed system coordination face significant risk from this vulnerability. The crash condition affects not only individual systems but can potentially cascade through networked environments where multiple devices rely on consistent time sources. This vulnerability aligns with ATT&CK technique T1499.001 which involves network denial of service attacks targeting network infrastructure services. The weakness can be particularly damaging in environments where precise timing is crucial for security event correlation, audit trails, and compliance requirements.
Mitigation strategies for CVE-2019-6445 primarily focus on upgrading to NTPsec version 1.1.3 or later where the NULL pointer dereference has been resolved through proper input validation and pointer checking. System administrators should implement access controls to limit who can submit control commands to the ntpd daemon, reducing the attack surface for authenticated attackers. Network segmentation and firewall rules can be configured to restrict control interface access to trusted management networks only. Additionally, monitoring systems should be deployed to detect unusual ntpd process restarts or crash patterns that might indicate exploitation attempts. Organizations should also consider implementing intrusion detection systems that can identify malformed control messages targeting the specific vulnerable function. The fix implemented in version 1.1.3 demonstrates proper defensive programming practices by ensuring all pointers are validated before dereferencing, which aligns with CWE recommendations for preventing null pointer dereference conditions through proper input validation and error handling mechanisms.