CVE-2012-4621 in IOS
Summary
by MITRE
The Device Sensor feature in Cisco IOS 15.0 through 15.2 allows remote attackers to cause a denial of service (device reload) via a DHCP packet, aka Bug ID CSCty96049.
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Analysis
by VulDB Data Team • 04/14/2021
The vulnerability described in CVE-2012-4621 represents a critical denial of service flaw within Cisco IOS software versions 15.0 through 15.2 that affects the Device Sensor feature. This vulnerability specifically targets the handling of DHCP packets within the network infrastructure, creating a scenario where remote attackers can trigger a complete device reload. The Device Sensor functionality in Cisco IOS is designed to monitor and manage network devices by collecting information about connected devices through various protocols including DHCP. When a malformed or specially crafted DHCP packet is received by a vulnerable device, it causes the system to enter an unstable state that ultimately results in an automatic device reboot. This behavior fundamentally undermines the availability of network services and can be exploited to disrupt critical network operations.
The technical mechanism behind this vulnerability involves improper input validation within the DHCP processing module of the Device Sensor feature. When a DHCP packet is received, the system fails to properly validate the packet structure and contents before processing it through the sensor subsystem. This lack of proper validation allows an attacker to craft specific DHCP packets that contain malformed data or unexpected values that cause the device to crash during processing. The vulnerability is particularly concerning because it operates at the network protocol level where attackers can exploit it remotely without requiring physical access or authentication credentials. The attack vector specifically leverages the DHCP protocol which is fundamental to network operations and is typically processed automatically by network devices without user intervention. This makes the vulnerability particularly dangerous as it can be triggered by any device attempting to connect to the network or by malicious actors who craft specific packets to exploit the flaw.
The operational impact of this vulnerability extends beyond simple device downtime, potentially causing cascading failures throughout network infrastructure. When a device reload occurs, it can disrupt network connectivity for all devices relying on that particular network element, leading to service degradation or complete network outages. Network administrators may experience significant operational challenges as the device automatically reboots, requiring manual intervention to restore normal operations. The vulnerability also creates opportunities for more sophisticated attacks where attackers might use the device reload as a stepping stone for additional exploitation attempts. Organizations relying on Cisco IOS devices for critical network operations face substantial risk from this vulnerability, as the timing of such attacks can be particularly damaging during peak network usage periods or critical business operations.
Organizations affected by this vulnerability should implement immediate mitigation strategies to protect their network infrastructure. The most effective approach involves applying the relevant Cisco security patches and updates that address the specific input validation flaws in the Device Sensor feature. Network administrators should also consider implementing network segmentation and access control measures to limit the potential impact of such attacks. Monitoring network traffic for unusual DHCP packet patterns and implementing intrusion detection systems can help identify exploitation attempts before they succeed. The vulnerability aligns with CWE-129, which addresses improper validation of input boundaries, and represents a classic example of how protocol parsing flaws can lead to denial of service conditions. From an ATT&CK framework perspective, this vulnerability maps to the T1499.004 technique related to network denial of service attacks, and could potentially be used as part of broader attack chains targeting network infrastructure availability. Organizations should also review their network device configurations to disable unnecessary Device Sensor functionality when not required, reducing the attack surface and limiting potential exploitation opportunities.