CVE-2025-5671 is a critical buffer overflow vulnerability identified in the TOTOLINK N302R Plus router, specifically affecting firmware versions up to 3.4.0-B20201028. The vulnerability resides in an unspecified function within the HTTP POST request handler component, located at the /boafrm/formPortFw endpoint. The issue arises from improper handling of the 'service_type' argument, which can be manipulated by an attacker to trigger a buffer overflow condition. This flaw allows remote attackers to potentially execute arbitrary code or cause a denial of service without requiring authentication or user interaction. The vulnerability has been publicly disclosed, increasing the risk of exploitation, although no known exploits are currently observed in the wild. The CVSS 4.0 base score is 8.7, indicating high severity, with attack vector being network-based, low attack complexity, no privileges or user interaction required, and high impact on confidentiality, integrity, and availability. The vulnerability's exploitation could lead to full compromise of the affected device, enabling attackers to control network traffic, intercept sensitive data, or launch further attacks within the network.

For European organizations, this vulnerability poses a significant risk, especially for those relying on TOTOLINK N302R Plus routers in their network infrastructure. Successful exploitation could lead to unauthorized access to internal networks, interception of sensitive communications, and disruption of network services. Given the router's role as a gateway device, compromise could facilitate lateral movement, data exfiltration, or serve as a foothold for broader cyberattacks. Small and medium enterprises (SMEs) and home office environments using this device are particularly vulnerable due to typically less rigorous network security controls. Additionally, critical sectors such as healthcare, finance, and government agencies could face severe operational and reputational damage if their network perimeter is breached via this vulnerability.

Organizations should immediately verify if TOTOLINK N302R Plus devices running firmware version 3.4.0-B20201028 or earlier are deployed within their environments. Since no official patches are currently linked, it is crucial to implement compensating controls: 1) Restrict remote access to the router's management interface by limiting access to trusted IP addresses or disabling remote management entirely. 2) Employ network segmentation to isolate vulnerable devices from critical assets. 3) Monitor network traffic for unusual POST requests targeting /boafrm/formPortFw or anomalous behavior indicative of exploitation attempts. 4) Consider replacing affected devices with models from vendors providing timely security updates. 5) Stay updated with TOTOLINK advisories for forthcoming patches and apply them promptly once available. 6) Implement intrusion detection/prevention systems (IDS/IPS) with signatures targeting this vulnerability to detect and block exploitation attempts.