CVE-2019-6472 in DHCPv6
Summary
by MITRE
A packet containing a malformed DUID can cause the Kea DHCPv6 server process (kea-dhcp6) to exit due to an assertion failure. 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 vulnerability described in CVE-2019-6472 represents a critical assertion failure in the Kea DHCPv6 server implementation that can lead to unauthorized service disruption. This issue specifically affects the kea-dhcp6 process which handles dhcpv6 protocol operations for network infrastructure. The flaw manifests when the server receives a packet containing a malformed DUID (DHCP Unique Identifier) which is a critical component used in dhcpv6 communications to uniquely identify clients and servers within the network. The DUID structure follows specific standards defined in rfc 3315 and rfc 4361, where proper formatting is essential for correct protocol operation and security. When the Kea server encounters an improperly formatted DUID, it triggers an assertion failure that causes the process to terminate unexpectedly, resulting in a denial of service condition for legitimate dhcpv6 clients seeking network configuration services.
The technical root cause of this vulnerability lies in insufficient input validation within the dhcpv6 server's packet processing logic. According to the common weakness enumeration framework, this represents a weakness categorized under cwe-248, which deals with an exception being thrown for an unusual circumstance but not properly handled. The assertion failure occurs during the parsing and validation of DUID fields within incoming dhcpv6 packets, where the server does not adequately sanitize or validate the DUID structure before proceeding with further processing. This lack of proper error handling means that malformed DUID values can cause the server to abruptly terminate rather than gracefully handling the invalid input and continuing operation. The vulnerability affects specific versions of the Kea software including 1.4.0 through 1.5.0 and the beta releases 1.6.0-beta1 and 1.6.0-beta2, indicating this was a known issue that persisted across multiple release cycles before being addressed.
The operational impact of CVE-2019-6472 extends beyond simple service disruption to potentially compromise network infrastructure reliability and availability. When the kea-dhcp6 process terminates due to assertion failure, all dhcpv6 services become unavailable until the process is manually restarted or automatically recovered by system monitoring tools. This can affect large networks where dhcpv6 is critical for ipv6 address allocation, especially in enterprise environments where network infrastructure depends on continuous availability. The vulnerability can be exploited by attackers who send specially crafted packets containing malformed DUID values, making it a remote denial of service attack vector. In the context of the attack tactics, techniques, and procedures framework, this vulnerability maps to the denial of service category under the network service disruption tactics, specifically targeting the availability aspect of the CIA triad. Organizations using Kea DHCPv6 servers in production environments face significant risk of service interruptions that can cascade into broader network operations issues.
Mitigation strategies for CVE-2019-6472 should focus on both immediate remediation and long-term architectural improvements. The primary and most effective mitigation is upgrading to Kea versions that have patched this vulnerability, typically versions 1.6.0 or later where proper input validation has been implemented for DUID processing. Network administrators should also implement packet filtering rules at network boundaries to drop dhcpv6 packets containing suspicious DUID structures, though this approach has limitations since it may block legitimate traffic. Additional defensive measures include implementing process monitoring and automatic restart mechanisms for the kea-dhcp6 service to minimize downtime when failures occur. Organizations should also consider implementing network segmentation to isolate dhcpv6 services and limit the potential impact of such attacks. The vulnerability highlights the importance of robust input validation and proper error handling in network infrastructure software, as outlined in various security frameworks including the owasp top 10 and nist cybersecurity framework. Regular security assessments and penetration testing should be conducted to identify similar input validation weaknesses in other network services that may be vulnerable to similar assertion failure scenarios.