CVE-2017-3864 in IOS
Summary
by MITRE
A vulnerability in the DHCP client implementation of Cisco IOS (12.2, 12.4, and 15.0 through 15.6) and Cisco IOS XE (3.3 through 3.7) could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition. The vulnerability occurs during the parsing of a crafted DHCP packet. An attacker could exploit this vulnerability by sending crafted DHCP packets to an affected device that is configured as a DHCP client. A successful exploit could allow the attacker to cause a reload of an affected device, resulting in a DoS condition. This vulnerability affects Cisco devices that are running a vulnerable release of Cisco IOS or IOS XE Software and using a specific DHCP client configuration. Cisco Bug IDs: CSCuu43892.
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Analysis
by VulDB Data Team • 08/28/2024
The vulnerability identified as CVE-2017-3864 represents a critical denial of service flaw within the dynamic host configuration protocol client implementation of Cisco IOS and IOS XE software versions. This weakness specifically manifests in versions 12.2, 12.4, and 15.0 through 15.6 for IOS, alongside versions 3.3 through 3.7 for IOS XE, creating a widespread exposure across multiple product lines. The flaw resides in the packet parsing mechanism that processes incoming DHCP responses, where malformed or specially crafted DHCP packets can trigger unexpected behavior in the affected systems. The vulnerability operates at the network protocol level, targeting the fundamental DHCP client functionality that enables devices to automatically acquire network configuration parameters including IP addresses, subnet masks, and default gateways.
The technical exploitation of this vulnerability occurs when an unauthenticated remote attacker crafts specific DHCP packets designed to trigger a buffer overflow or memory corruption condition within the affected Cisco devices. During normal DHCP client operations, devices receive DHCP offers and acknowledge them through DHCP ack messages, but the vulnerable parsing code fails to properly validate incoming packet structures. When a maliciously constructed DHCP packet is received, the system's DHCP client module attempts to process the malformed data without adequate boundary checks, leading to memory corruption that ultimately causes the device to crash and restart. This behavior directly maps to CWE-121, which describes heap-based buffer overflow conditions, and aligns with ATT&CK technique T1499.002 for network denial of service attacks. The attack vector requires no authentication and can be executed from remote locations, making it particularly dangerous for network infrastructure devices.
The operational impact of this vulnerability extends beyond simple service disruption, as the DoS condition results in complete device reloads that can cascade through network infrastructure and potentially compromise larger network segments. When affected devices restart, they lose their current network configuration and must reacquire network parameters through the DHCP process, creating temporary network outages that can affect critical services and applications. Network administrators may experience significant downtime as devices recover, and the frequency of such attacks can compound the disruption. The vulnerability affects devices that are actively configured as DHCP clients, meaning any Cisco equipment that connects to networks using DHCP for configuration, including routers, switches, and wireless access points. This makes the attack surface particularly broad across enterprise and service provider networks.
Mitigation strategies for CVE-2017-3864 require immediate attention from network administrators and security teams, with the most effective solution being the application of official Cisco patches and software updates. The vulnerability can be addressed through IOS software upgrades to versions that contain the necessary fixes, with Cisco releasing patches specifically designed to correct the DHCP client parsing logic. Network segmentation and access control measures can provide temporary protection by limiting the network segments where vulnerable devices can receive DHCP responses, though this approach does not eliminate the underlying flaw. Monitoring network traffic for unusual DHCP packet patterns and implementing intrusion detection systems that can identify malicious DHCP traffic can help detect exploitation attempts. Additionally, organizations should consider disabling DHCP client functionality on devices where it is not strictly required, and implementing redundant network paths to minimize the impact of device reloads. The vulnerability highlights the importance of maintaining current software versions and following vendor security advisories, as the affected software versions represent a significant risk to network availability and stability.