CVE-2019-6473 in DHCPv4
Summary
by MITRE
An invalid hostname option can trigger an assertion failure in the Kea DHCPv4 server process (kea-dhcp4), causing the server process to exit. Versions affected: 1.4.0 to 1.5.0, 1.6.0-beta1, and 1.6.0-beta2.
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Analysis
by VulDB Data Team • 01/16/2024
The CVE-2019-6473 vulnerability represents a critical assertion failure in the Kea DHCPv4 server implementation that can lead to remote denial of service conditions. This issue specifically affects the kea-dhcp4 process which serves as the core DHCPv4 server component in the Kea DHCP suite. The vulnerability manifests when an invalid hostname option is processed during DHCP communication, causing the server to abruptly terminate its operation through an assertion failure mechanism. This type of vulnerability falls under the category of software quality assurance failures where proper input validation and error handling mechanisms are insufficient to prevent system crashes.
The technical flaw stems from inadequate validation of hostname options within the DHCPv4 server's processing pipeline. When the kea-dhcp4 process encounters a malformed or invalid hostname option in a DHCP request, it fails to properly handle this edge case through graceful error recovery mechanisms. Instead, the server triggers an assertion failure that results in immediate process termination. This behavior represents a classic example of improper error handling and input validation that can be exploited by attackers to cause service disruption. The vulnerability specifically affects versions ranging from 1.4.0 through 1.5.0 and includes the beta releases 1.6.0-beta1 and 1.6.0-beta2, indicating this was a persistent issue within the Kea DHCP server development cycle.
The operational impact of CVE-2019-6473 extends beyond simple service interruption to potentially compromise network infrastructure availability. When the kea-dhcp4 process terminates due to assertion failure, all DHCP services provided by that server instance become unavailable until manual intervention occurs to restart the service. This can result in widespread network disruption as client devices lose the ability to obtain IP addresses dynamically, effectively creating a denial of service condition. Network administrators may experience cascading failures if multiple DHCP servers are affected or if the service interruption impacts critical network operations. The vulnerability can be triggered remotely by any entity capable of sending malformed DHCP packets to the affected server, making it particularly dangerous in network environments where DHCP servers are exposed to untrusted networks.
Mitigation strategies for CVE-2019-6473 focus primarily on upgrading to patched versions of the Kea DHCP server software where the assertion failure has been resolved through proper input validation and error handling mechanisms. Organizations should prioritize immediate deployment of version 1.6.0 or later releases that contain the necessary fixes for this vulnerability. Additionally, network administrators can implement monitoring solutions to detect unusual process termination patterns and establish automated alerting systems for DHCP service disruptions. The vulnerability demonstrates the importance of robust input validation and error handling practices in network infrastructure software, aligning with common weakness enumerations such as CWE-248 and attack techniques described in MITRE ATT&CK framework under T1499 for network denial of service attacks. Network segmentation and access control measures can provide additional defense-in-depth layers to limit exposure of vulnerable DHCP servers to untrusted network segments while the primary fix is implemented.