CVE-2021-32771 is a medium-severity vulnerability classified under CWE-120, which refers to a classic buffer overflow due to improper bounds checking during buffer copy operations. This vulnerability affects Contiki-NG, an open-source, cross-platform operating system widely used in Internet of Things (IoT) devices, particularly those implementing IPv6 networking and RPL (Routing Protocol for Low-Power and Lossy Networks). The flaw exists in the RPL-Classic implementation within Contiki-NG versions prior to 4.8. Specifically, when a Contiki-NG device has joined an RPL DODAG (Destination-Oriented Directed Acyclic Graph), an attacker can send a DAO (Destination Advertisement Object) packet containing a Target option with a prefix length exceeding 128 bits. Since IPv6 addresses are 128 bits in length, this malformed prefix length causes a buffer overflow during the copying of the IPv6 address prefix. This unchecked buffer copy can lead to memory corruption, potentially allowing an attacker to execute arbitrary code, cause a denial of service (DoS) through system crashes, or disrupt network routing functionality. The vulnerability requires the device to be part of an RPL network and reachable by an attacker capable of sending crafted DAO packets. The issue was resolved in Contiki-NG version 4.8, and a patch is available via Contiki-NG pull request #1615 for users unable to upgrade immediately. There are no known exploits in the wild as of the publication date, but the vulnerability presents a significant risk due to the nature of buffer overflows and the critical role of RPL in IoT network routing.

For European organizations deploying IoT devices running Contiki-NG, especially in critical infrastructure sectors such as smart cities, industrial automation, energy management, and healthcare, this vulnerability poses a risk of network disruption and potential device compromise. Exploitation could lead to denial of service conditions in IoT networks, affecting availability and reliability of services. In worst-case scenarios, attackers might achieve remote code execution, compromising device integrity and confidentiality of data transmitted over the network. Given the increasing adoption of IPv6 and RPL in constrained IoT environments across Europe, the vulnerability could be leveraged to disrupt large-scale IoT deployments. This is particularly concerning for organizations relying on IoT for operational technology (OT) environments where safety and continuous operation are critical. The attack vector requires network access to the RPL DODAG, so exposure depends on network segmentation and device accessibility. However, once exploited, the impact could cascade through interconnected IoT systems, affecting broader organizational operations.

1. Upgrade all Contiki-NG deployments to version 4.8 or later, which contains the official fix for this vulnerability. 2. For environments where immediate upgrade is not feasible, apply the patch provided in Contiki-NG pull request #1615 to address the buffer overflow. 3. Implement strict network segmentation and access controls to limit exposure of RPL networks to untrusted or external sources, reducing the attack surface. 4. Monitor network traffic for anomalous DAO packets with unusual prefix lengths or malformed RPL control messages, using specialized IoT network monitoring tools. 5. Employ intrusion detection systems (IDS) capable of parsing RPL protocol traffic to detect and alert on suspicious activity targeting RPL DODAGs. 6. Conduct regular security audits and firmware integrity checks on IoT devices running Contiki-NG to ensure patches are applied and no unauthorized modifications exist. 7. Collaborate with IoT device vendors and integrators to ensure secure configuration and timely patch management of Contiki-NG-based devices. 8. Consider deploying network-level mitigations such as rate limiting and packet validation to prevent malformed DAO packets from reaching vulnerable devices.