RIOT-OS is an open-source operating system tailored for IoT and embedded devices, supporting IPv6 networking including fragmentation and reassembly. In versions before 2025.10, the IPv6 fragmentation reassembly code (specifically the gnrc_ipv6_ext_frag module) contains a classic buffer overflow vulnerability (CWE-120). When processing fragmented IPv6 packets, the system copies the first fragment (offset=0) into a reassembly buffer without verifying that the fragment size fits within the allocated buffer. An attacker can first send a smaller fragment to force the creation of a smaller reassembly buffer, then send a larger fragment to overflow this buffer. This overflow corrupts the state of adjacent packet buffers, which may be leveraged to cause further memory corruption and potentially achieve remote code execution on the device. Exploitation requires no privileges or user interaction but does require the attacker to send crafted IPv6 packets to the device. The vulnerability is mitigated by updating to RIOT-OS version 2025.10, where proper size checks are implemented. No public exploits or widespread attacks have been reported, and the CVSS 4.0 score is 1.7, reflecting low severity due to limited impact and exploitation complexity.

For European organizations deploying IoT devices running vulnerable versions of RIOT-OS, this vulnerability poses a risk of device compromise through remote code execution. Such devices are often used in critical infrastructure, industrial control systems, smart city applications, and healthcare monitoring, where device integrity and availability are paramount. Exploitation could lead to unauthorized control, data manipulation, or denial of service, potentially disrupting operations or compromising sensitive data. Given the low CVSS score, the immediate risk is limited, but the potential for escalation in complex IoT environments exists. The impact is higher in scenarios where devices are exposed to untrusted IPv6 networks or where network segmentation is weak. European organizations with large IoT deployments should consider this vulnerability seriously, especially in sectors with high reliance on embedded systems.

1. Upgrade all RIOT-OS deployments to version 2025.10 or later, where the vulnerability is patched. 2. Disable the gnrc_ipv6_ext_frag module if IPv6 fragmentation is not required in the deployment environment to reduce the attack surface. 3. Implement strict network segmentation and firewall rules to limit exposure of IoT devices to untrusted IPv6 traffic, especially from external networks. 4. Monitor network traffic for anomalous IPv6 fragmentation patterns that could indicate exploitation attempts. 5. Employ intrusion detection systems capable of inspecting IPv6 fragmented packets for suspicious behavior. 6. Conduct regular firmware audits and vulnerability assessments on IoT devices to ensure timely patching and configuration compliance. 7. Collaborate with device manufacturers and vendors to ensure secure update mechanisms are in place for rapid deployment of patches.