CVE-2024-20480 in IOS XE
Summary
by MITRE • 09/25/2024
A vulnerability in the DHCP Snooping feature of Cisco IOS XE Software on Software-Defined Access (SD-Access) fabric edge nodes could allow an unauthenticated, remote attacker to cause high CPU utilization on an affected device, resulting in a denial of service (DoS) condition that requires a manual reload to recover.
This vulnerability is due to improper handling of IPv4 DHCP packets. An attacker could exploit this vulnerability by sending certain IPv4 DHCP packets to an affected device. A successful exploit could allow the attacker to cause the device to exhaust CPU resources and stop processing traffic, resulting in a DoS condition that requires a manual reload to recover.
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Analysis
by VulDB Data Team • 01/02/2025
The vulnerability identified as CVE-2024-20480 resides within the DHCP Snooping functionality of Cisco IOS XE Software operating on Software-Defined Access SD-Access fabric edge nodes. This represents a critical denial of service weakness that can be exploited remotely without authentication, targeting the core network infrastructure components that manage device access and network segmentation. The affected devices operate as edge nodes within SD-Access fabric environments, which are designed to provide automated network access control and policy enforcement across enterprise networks. These edge nodes serve as critical points of network entry and exit, making their stability essential for overall network operations and service availability.
The technical flaw stems from inadequate validation and processing of IPv4 DHCP packets within the DHCP Snooping implementation. When malformed or specially crafted DHCP packets are received by the affected device, the system fails to properly handle these packets, leading to excessive CPU utilization as the device attempts to process these malformed inputs. This improper packet handling creates a resource exhaustion condition where the CPU becomes overwhelmed with processing tasks that should be simple validation operations. The vulnerability specifically affects the DHCP Snooping mechanism which is designed to prevent unauthorized DHCP servers from operating within the network and to maintain network security policies. The flaw manifests as a continuous loop or excessive processing of DHCP packet fields that trigger the device's CPU to consume resources at an unsustainable rate, ultimately leading to complete service disruption.
The operational impact of this vulnerability extends beyond simple service interruption, as it affects the fundamental network infrastructure that supports enterprise connectivity and access control. Network administrators face the challenging scenario of having to manually reload affected devices to restore normal operations, which results in service interruptions that can last from several minutes to hours depending on the device's recovery process. This vulnerability particularly threatens SD-Access environments where edge nodes are critical for maintaining network segmentation policies and automated access control. The DoS condition affects not just individual devices but can potentially cascade through the fabric network, as edge nodes are often interconnected and their failure can disrupt broader network operations. Organizations relying on SD-Access fabric for network automation and policy enforcement face significant operational risks, as the vulnerability can be exploited by attackers without requiring any credentials or network access privileges.
Mitigation strategies for CVE-2024-20480 should focus on immediate patch deployment and network segmentation controls. Cisco has released software updates that address this vulnerability through enhanced packet validation and improved error handling within the DHCP Snooping implementation. Network administrators should prioritize applying these patches to all affected edge nodes within their SD-Access fabric environments. Additionally, implementing network access controls to limit DHCP packet sources can provide temporary protection while patches are deployed. The vulnerability aligns with CWE-129, which addresses improper validation of input boundaries, and can be categorized under ATT&CK technique T1499.004 for network denial of service attacks. Organizations should also consider implementing monitoring solutions that can detect unusual CPU utilization patterns and DHCP packet processing anomalies to provide early warning of potential exploitation attempts. The remediation process requires careful planning due to the critical nature of SD-Access edge nodes, ensuring that patch deployment does not disrupt ongoing network operations while maintaining security posture against this specific DoS vulnerability.