CVE-2024-20446 in NX-OS
Summary
by MITRE • 08/28/2024
A vulnerability in the DHCPv6 relay agent of Cisco NX-OS Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device.
This vulnerability is due to improper handling of specific fields in a DHCPv6 RELAY-REPLY message. An attacker could exploit this vulnerability by sending a crafted DHCPv6 packet to any IPv6 address that is configured on an affected device. A successful exploit could allow the attacker to cause the dhcp_snoop process to crash and restart multiple times, causing the affected device to reload and resulting in a DoS condition.
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Analysis
by VulDB Data Team • 08/29/2024
The vulnerability identified as CVE-2024-20446 represents a critical denial of service weakness within Cisco NX-OS Software's DHCPv6 relay agent implementation. This flaw specifically targets the processing of DHCPv6 RELAY-REPLY messages, where the system fails to properly validate or handle certain field values in incoming packets. The vulnerability affects network infrastructure devices running Cisco NX-OS Software that have IPv6 addressing configured, making it particularly concerning for enterprise networks that rely on DHCPv6 for address allocation and network services. The improper field handling creates a condition where malformed or specially crafted DHCPv6 packets can trigger unexpected behavior in the software's packet processing logic.
The technical exploitation of this vulnerability occurs through the transmission of specifically crafted DHCPv6 packets to any IPv6 address configured on the affected device. The attack vector is particularly dangerous because it requires no authentication credentials, making it accessible to any remote attacker with network connectivity to the target device. When the DHCPv6 relay agent receives these malformed packets, the processing logic fails to properly validate the packet structure, leading to a crash in the dhcp_snoop process. This process is responsible for managing DHCP snooping operations and maintaining the integrity of DHCP communications within the network. The crash condition causes the process to restart multiple times in rapid succession, creating a cascading failure that eventually leads to a complete device reload.
The operational impact of this vulnerability extends beyond simple service disruption, as the repeated process crashes and device reloads can result in significant network downtime and potential service interruptions for connected devices. Network administrators may experience extended periods of unavailability as the device recovers from the repeated crashes, and the automatic reload process can cause temporary loss of network connectivity for hosts relying on the affected device for routing and forwarding services. The vulnerability's remote nature means that attackers can exploit it from outside the network perimeter, making it particularly dangerous for devices that are exposed to public internet access or have insufficient network segmentation controls. This weakness can be especially problematic in mission-critical environments where network availability is paramount, as the DoS condition can persist until manual intervention or automatic recovery mechanisms are triggered.
Organizations should implement immediate mitigations including applying the latest security patches provided by Cisco, which address the improper field handling in DHCPv6 packet processing. Network segmentation strategies should be employed to limit exposure of affected devices to untrusted networks, while implementing access control lists to filter DHCPv6 traffic at network boundaries. Monitoring should be enhanced to detect unusual patterns in DHCPv6 packet processing and process restart events, which can serve as early warning indicators of potential exploitation attempts. The vulnerability aligns with CWE-129, which addresses improper validation of input boundaries, and relates to ATT&CK technique T1499.004 for network disruption attacks. Organizations should also consider implementing network intrusion detection systems that can identify and alert on suspicious DHCPv6 packet patterns that match the vulnerability characteristics, providing additional layers of defense beyond the primary patching and configuration controls.