CVE-2025-51630 is a buffer overflow vulnerability identified in the TOTOLINK N350RT router firmware version 9.3.5u.6139_B20201216. The vulnerability arises from improper handling of the ePort parameter within the setIpPortFilterRules function. Buffer overflow vulnerabilities occur when a program writes more data to a buffer than it can hold, potentially overwriting adjacent memory. In this case, an attacker could craft a malicious request targeting the ePort parameter to trigger the overflow. Exploiting this vulnerability could allow an attacker to execute arbitrary code, cause a denial of service (DoS) by crashing the device, or manipulate the router’s operation. Since the vulnerability is in a network device’s firmware, exploitation could be performed remotely if the affected function is accessible via the network interface, increasing the risk. No CVSS score has been assigned yet, and no known exploits are reported in the wild. The vulnerability was reserved in mid-June 2025 and published in July 2025, indicating recent discovery. TOTOLINK N350RT is a consumer-grade wireless router commonly used in home and small office environments. The lack of a patch link suggests that a fix may not yet be available, emphasizing the importance of mitigation and monitoring. The technical details do not specify whether authentication or user interaction is required, but given the nature of the function (port filtering rules), it may be accessible via the router’s management interface or exposed services, which could be remotely exploitable if not properly secured.

For European organizations, the impact of this vulnerability depends on the deployment scale of TOTOLINK N350RT routers within their networks. Small businesses and home offices using this router model could be at risk of unauthorized access, network disruption, or compromise of internal network traffic. Exploitation could lead to loss of confidentiality if attackers gain access to network traffic or device credentials, integrity loss if firewall or port filtering rules are manipulated, and availability issues if the router is crashed or rendered inoperable. Given that routers are critical network infrastructure, compromise could facilitate lateral movement, data exfiltration, or serve as a foothold for further attacks. The absence of known exploits reduces immediate risk but does not eliminate it, especially as proof-of-concept code may emerge. European organizations with remote management enabled or exposed management interfaces are particularly vulnerable. Additionally, the potential for exploitation without authentication (if applicable) would increase risk significantly. The threat is more pronounced for sectors with high reliance on secure network infrastructure, such as finance, healthcare, and government agencies operating in Europe.

1. Immediate mitigation should include restricting access to the router’s management interface by disabling remote management or limiting it to trusted IP addresses. 2. Network segmentation should be enforced to isolate vulnerable devices from critical systems. 3. Monitor network traffic for unusual activity or attempts to exploit the ePort parameter. 4. Apply any available firmware updates from TOTOLINK as soon as they are released. 5. If no patch is available, consider replacing vulnerable routers with models from vendors with timely security support. 6. Implement strong authentication mechanisms for router management interfaces, including complex passwords and, if supported, multi-factor authentication. 7. Regularly audit router configurations to ensure port filtering rules and other security settings have not been tampered with. 8. Employ intrusion detection/prevention systems (IDS/IPS) to detect exploitation attempts targeting this vulnerability. 9. Educate IT staff about the vulnerability and ensure incident response plans include steps for router compromise scenarios.