CVE-2025-4835 is a critical buffer overflow vulnerability affecting TOTOLINK router models A702R, A3002R, and A3002RU running firmware version 3.0.0-B20230809.1615. The flaw exists in the HTTP POST request handler component, specifically in the /boafrm/formWlanRedirect endpoint. An attacker can manipulate the 'redirect-url' parameter in the POST request to trigger a buffer overflow condition. This vulnerability is remotely exploitable without requiring user interaction or prior authentication, making it highly dangerous. The buffer overflow can lead to arbitrary code execution or cause the device to crash, potentially resulting in denial of service or full compromise of the router. The CVSS 4.0 base score is 8.7 (high severity), reflecting the ease of remote exploitation and the high impact on confidentiality, integrity, and availability. Although no public exploits are currently known to be active in the wild, the disclosure of the vulnerability and its exploit details increases the risk of imminent attacks. The vulnerability affects a core network device that manages traffic routing and wireless access, making it a critical point of failure in network infrastructure.

For European organizations, this vulnerability poses a significant risk to network security and operational continuity. TOTOLINK routers are commonly used in small to medium enterprises and some home office environments across Europe. Successful exploitation could allow attackers to gain control over the router, intercept or manipulate network traffic, and potentially pivot to internal systems. This could lead to data breaches, disruption of business operations, and compromise of sensitive information. Critical infrastructure providers and organizations relying on these routers for secure internet access are particularly vulnerable. The lack of authentication and user interaction requirements means attackers can launch attacks remotely and at scale, increasing the threat landscape. Additionally, compromised routers could be enlisted in botnets or used to launch further attacks against European networks.

Organizations should immediately verify if their TOTOLINK devices are running the affected firmware version 3.0.0-B20230809.1615. If so, they should seek firmware updates or patches from TOTOLINK as a priority. In the absence of an official patch, network administrators should restrict access to the router's management interface by implementing IP-based access controls, disabling remote management, and isolating the device from untrusted networks. Monitoring network traffic for unusual POST requests to /boafrm/formWlanRedirect can help detect exploitation attempts. Employing network intrusion detection systems (NIDS) with signatures for this vulnerability is recommended. Additionally, organizations should consider replacing vulnerable devices with models from vendors with a stronger security track record if patching is delayed. Regularly auditing router configurations and applying the principle of least privilege to network devices will further reduce risk.