CVE-2017-12240 in IOS
Summary
by MITRE
The DHCP relay subsystem of Cisco IOS 12.2 through 15.6 and Cisco IOS XE Software contains a vulnerability that could allow an unauthenticated, remote attacker to execute arbitrary code and gain full control of an affected system. The attacker could also cause an affected system to reload, resulting in a denial of service (DoS) condition. The vulnerability is due to a buffer overflow condition in the DHCP relay subsystem of the affected software. An attacker could exploit this vulnerability by sending a crafted DHCP Version 4 (DHCPv4) packet to an affected system. A successful exploit could allow the attacker to execute arbitrary code and gain full control of the affected system or cause the affected system to reload, resulting in a DoS condition. Cisco Bug IDs: CSCsm45390, CSCuw77959.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 09/09/2024
The vulnerability identified as CVE-2017-12240 resides within the DHCP relay subsystem of Cisco IOS versions 12.2 through 15.6 and Cisco IOS XE Software, representing a critical security flaw that exposes network infrastructure to remote exploitation. This vulnerability falls under the Common Weakness Enumeration category CWE-121, which describes a buffer overflow condition where insufficient bounds checking allows an attacker to overwrite adjacent memory locations. The affected systems operate with a fundamental design flaw in their DHCP relay implementation that fails to properly validate input data from DHCP Version 4 packets, creating an exploitable entry point for malicious actors.
The technical exploitation mechanism involves an attacker crafting specifically formatted DHCPv4 packets that trigger a buffer overflow within the DHCP relay component. This overflow condition occurs when the system receives a malformed packet that exceeds the allocated buffer space, causing adjacent memory to be overwritten with attacker-controlled data. The vulnerability is particularly dangerous because it allows for arbitrary code execution without requiring authentication, making it accessible to anyone who can send packets to the affected network device. The exploit chain typically begins with sending a malicious DHCP packet that causes the buffer overflow, which then leads to instruction pointer corruption and subsequent code execution.
The operational impact of this vulnerability extends beyond simple code execution to include complete system compromise and potential denial of service conditions. An attacker who successfully exploits this vulnerability can gain full administrative control over the affected Cisco device, enabling them to modify network configurations, intercept traffic, or establish persistent backdoors within the network infrastructure. The system reload functionality provides an additional attack vector for denial of service, allowing attackers to repeatedly disrupt network services by causing the device to continuously reboot. This dual capability makes the vulnerability particularly attractive to threat actors seeking both persistent access and disruption capabilities.
Cisco has documented this vulnerability through bug IDs CSCsm45390 and CSCuw77959, indicating the severity and complexity of the issue. Network administrators should implement immediate mitigations including applying the latest security patches released by Cisco, configuring access control lists to restrict DHCP traffic, and monitoring network traffic for suspicious DHCP packets. The ATT&CK framework categorizes this vulnerability under T1059.007 for command and scripting interpreter and T1499.004 for network disruption, highlighting both the execution and impact phases of potential attacks. Organizations should also consider implementing network segmentation to limit the blast radius of such attacks and deploy intrusion detection systems capable of identifying malformed DHCP packets that could indicate exploitation attempts.