CVE-2025-8170 is a critical buffer overflow vulnerability identified in the TOTOLINK T6 router, specifically version 4.1.5cu.748_B20211015. The flaw exists in the tcpcheck_net function within the /router/meshSlaveDlfw component, which handles MQTT packets. The vulnerability arises when the serverIp argument is manipulated, leading to a buffer overflow condition. This type of vulnerability can allow an attacker to overwrite memory, potentially enabling arbitrary code execution or causing denial of service. The vulnerability is remotely exploitable without requiring user interaction or prior authentication, increasing its risk profile. The CVSS 4.0 base score is 8.7 (high severity), reflecting its network attack vector, low complexity, no privileges or user interaction needed, but with high impact on confidentiality, integrity, and availability. Although no public exploits are currently known in the wild, the exploit code has been disclosed publicly, which may increase the likelihood of exploitation attempts. The vulnerability affects a widely deployed consumer and small office router model, which is often used as a network gateway device, making it a critical point of compromise if exploited. The MQTT packet handler is a core component for IoT and mesh networking features, so exploitation could disrupt network communications or allow attackers to pivot into internal networks.

For European organizations, this vulnerability poses a significant risk due to the widespread use of TOTOLINK T6 routers in small and medium enterprises as well as home office environments. Successful exploitation could lead to full compromise of the router, allowing attackers to intercept, modify, or disrupt network traffic, potentially leading to data breaches, espionage, or ransomware deployment. The high impact on confidentiality, integrity, and availability means sensitive corporate data and communications could be exposed or manipulated. Additionally, compromised routers could be leveraged as entry points for lateral movement into corporate networks or as part of botnets for further attacks. Given the remote exploitability and lack of authentication requirements, attackers can target vulnerable devices over the internet, increasing the threat surface. European organizations relying on these devices for critical connectivity or IoT integration are particularly vulnerable to operational disruptions and data loss.

Organizations should immediately identify all TOTOLINK T6 routers running the affected firmware version 4.1.5cu.748_B20211015. Since no official patches are currently linked, it is critical to check TOTOLINK’s official channels regularly for firmware updates addressing this vulnerability. In the interim, network administrators should restrict remote access to the router’s management interfaces, especially MQTT services, by implementing strict firewall rules and network segmentation to isolate vulnerable devices from critical infrastructure. Disabling MQTT or mesh networking features if not required can reduce the attack surface. Monitoring network traffic for unusual MQTT packets or signs of exploitation attempts is recommended. Employing intrusion detection/prevention systems (IDS/IPS) with signatures targeting this vulnerability can help detect and block attacks. Organizations should also consider replacing vulnerable devices with models from vendors with active security support if patches are delayed. Finally, maintaining up-to-date asset inventories and vulnerability management processes will ensure timely response to emerging threats.