CVE-2018-0174 in IOS
Summary
by MITRE
A vulnerability in the DHCP option 82 encapsulation functionality of Cisco IOS Software and Cisco IOS XE Software could allow an unauthenticated, remote attacker to cause an affected device to reload, resulting in a denial of service (DoS) condition. The vulnerability exists because the affected software performs incomplete input validation of option 82 information that it receives in DHCP Version 4 (DHCPv4) packets from DHCP relay agents. An attacker could exploit this vulnerability by sending a crafted DHCPv4 packet to an affected device. A successful exploit could allow the attacker to cause the affected device to reload, resulting in a DoS condition. Cisco Bug IDs: CSCuh91645.
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Analysis
by VulDB Data Team • 09/09/2024
The vulnerability described in CVE-2018-0174 represents a critical denial of service weakness within Cisco's networking infrastructure software, specifically affecting IOS and IOS XE operating systems. This flaw resides in the DHCP option 82 encapsulation functionality, which serves as a crucial component for managing network traffic in complex enterprise environments where DHCP relay agents are utilized. The vulnerability stems from insufficient input validation mechanisms that fail to properly sanitize or verify the option 82 data received in DHCPv4 packets, creating an exploitable condition that can be leveraged by remote attackers without requiring authentication credentials.
The technical implementation of this vulnerability involves the improper handling of DHCP option 82 information within the software's packet processing pipeline. When an affected Cisco device receives a DHCPv4 packet containing malformed or specially crafted option 82 data from a DHCP relay agent, the software's input validation routines fail to adequately process this information. This incomplete validation allows maliciously constructed packets to trigger unexpected behavior within the device's memory management and processing functions. The flaw specifically manifests during the parsing and encapsulation of DHCP option 82 data, where the system attempts to handle malformed fields or unexpected data structures that exceed expected parameters or buffer limits.
The operational impact of this vulnerability extends beyond simple service disruption, as it can result in complete device reloads that effectively deny network services to legitimate users. Network administrators face the significant challenge of maintaining service availability when an unauthenticated attacker can remotely trigger device reboots simply by sending specially crafted DHCP packets. This condition creates cascading effects throughout the network infrastructure, potentially disrupting critical business operations and requiring immediate remediation efforts. The vulnerability's remote exploitability means that attackers can target affected devices from outside the network perimeter, making it particularly dangerous for organizations with exposed network services or those utilizing DHCP relay functionality in their network design.
Mitigation strategies for CVE-2018-0174 should prioritize immediate software updates to address the input validation deficiencies in the DHCP option 82 processing functionality. Organizations must implement network segmentation controls to limit exposure of affected devices to untrusted network segments, particularly those that do not require DHCP relay functionality. Network administrators should consider implementing access control lists or firewall rules to filter DHCP traffic and restrict the sources of DHCP relay agents to trusted network segments. The vulnerability aligns with CWE-20, which describes improper input validation, and represents a typical example of how insufficient validation of externally supplied data can lead to system instability. From an ATT&CK framework perspective, this vulnerability maps to the T1499.004 technique related to network denial of service attacks, where adversaries leverage software weaknesses to disrupt network services. Additionally, the vulnerability demonstrates the importance of implementing proper defensive measures at network boundaries and maintaining up-to-date security patches to prevent exploitation of known weaknesses in network infrastructure software.