CVE-2025-67188 identifies a critical buffer overflow vulnerability in the TOTOLINK A950RG router firmware version V4.1.2cu.5204_B20210112. The vulnerability is located in the setRadvdCfg interface of the /lib/cste_modules/ipv6.so module, which handles configuration for the router's IPv6 router advertisement daemon (radvd). Specifically, the function fails to properly validate the length of the radvdinterfacename parameter, which is user-controlled input. This improper validation allows a remote attacker to send a specially crafted request that overflows the stack buffer, potentially overwriting adjacent memory. Such a stack buffer overflow can lead to arbitrary code execution or cause the device to crash, resulting in denial of service. The vulnerability can be triggered remotely without authentication or user interaction, increasing its risk profile. Although no known exploits have been reported in the wild and no patches are currently available, the vulnerability's presence in a widely used router model with IPv6 support makes it a significant threat. Attackers could leverage this flaw to gain control over the router, intercept or manipulate network traffic, or disrupt network availability. The lack of a CVSS score requires an assessment based on the technical details, which indicates a high severity due to the ease of exploitation and potential impact. Organizations should prioritize monitoring and mitigation efforts to reduce exposure until a vendor patch is released.

For European organizations, the impact of CVE-2025-67188 could be substantial. The TOTOLINK A950RG router is used in various enterprise and possibly consumer environments, particularly where IPv6 is deployed. Successful exploitation could allow attackers to execute arbitrary code on the router, leading to full compromise of the device. This could enable interception or manipulation of network traffic, insertion of malicious payloads, or disruption of network services, affecting confidentiality, integrity, and availability. Critical infrastructure, government agencies, and enterprises relying on these routers for perimeter or internal network routing could face operational disruptions or data breaches. The remote, unauthenticated nature of the exploit increases the risk of widespread attacks, especially if automated exploit tools emerge. The absence of patches means organizations must rely on network-level defenses and monitoring to mitigate risk. Additionally, the vulnerability could be leveraged as a foothold for lateral movement within networks, increasing the overall threat landscape for European entities.

1. Immediately restrict access to the TOTOLINK A950RG router management interfaces, especially from untrusted networks, by implementing strict firewall rules and network segmentation. 2. Disable IPv6 router advertisement services if not required, or limit their exposure to trusted internal networks only. 3. Monitor network traffic for unusual or malformed packets targeting the radvd interface or related IPv6 configuration services using intrusion detection/prevention systems (IDS/IPS). 4. Employ network anomaly detection tools to identify potential exploitation attempts based on buffer overflow signatures or abnormal behavior. 5. Maintain up-to-date inventory of network devices to identify all affected TOTOLINK routers and prioritize their monitoring. 6. Engage with the vendor for timely patch releases and apply firmware updates as soon as they become available. 7. Consider deploying compensating controls such as network access control (NAC) to limit device exposure. 8. Educate network administrators about this vulnerability and ensure incident response plans include steps for potential exploitation scenarios. 9. If possible, replace vulnerable devices with models from vendors with stronger security track records or with active patch support.