CVE-2025-6400 is a critical buffer overflow vulnerability identified in the TOTOLINK N300RH router, specifically affecting firmware version 6.1c.1390_B20191101. The vulnerability resides in the HTTP POST message handler component, within the /boafrm/formPortFw endpoint. An attacker can manipulate the 'service_type' argument in the POST request to trigger a buffer overflow condition. This flaw allows remote attackers to potentially execute arbitrary code or cause a denial of service without requiring user interaction or authentication. The vulnerability has a CVSS 4.0 base score of 8.7, indicating high severity, with an attack vector of network (remote), low attack complexity, no privileges required, and no user interaction needed. The impact metrics indicate high confidentiality, integrity, and availability impacts, meaning successful exploitation could lead to full compromise of the device. Although no public exploit is currently known to be actively used in the wild, the exploit details have been publicly disclosed, increasing the risk of exploitation. The TOTOLINK N300RH is a consumer-grade wireless router commonly deployed in small office and home environments, often used as a network gateway device. The buffer overflow in the HTTP POST handler suggests that crafted network traffic can be used to compromise the device remotely, potentially allowing attackers to gain control over the router, intercept or manipulate network traffic, or pivot into internal networks. Given the router’s role in network infrastructure, this vulnerability poses a significant risk to network security and privacy.

For European organizations, the exploitation of CVE-2025-6400 could lead to severe consequences. Compromised TOTOLINK N300RH routers can serve as entry points for attackers to infiltrate corporate or home networks, enabling data interception, traffic manipulation, or lateral movement to more critical systems. This is particularly concerning for small and medium enterprises (SMEs) and home offices that rely on consumer-grade routers without advanced security controls. The loss of confidentiality could expose sensitive business or personal data, while integrity and availability impacts could disrupt network operations, causing downtime and loss of productivity. Additionally, compromised routers could be leveraged in botnets or for launching further attacks, amplifying the threat landscape. The lack of authentication and user interaction requirements lowers the barrier for attackers, increasing the likelihood of exploitation. The public disclosure of the vulnerability further elevates risk, as attackers can develop and deploy exploits rapidly. Organizations using affected devices without timely firmware updates or mitigations are at heightened risk of compromise.

1. Immediate firmware update: TOTOLINK should be contacted to confirm availability of a patched firmware version addressing CVE-2025-6400. Organizations must prioritize upgrading all affected N300RH devices to the latest secure firmware. 2. Network segmentation: Isolate TOTOLINK N300RH routers from critical network segments to limit potential lateral movement if compromised. 3. Disable remote management: If remote HTTP management interfaces are enabled, disable them or restrict access to trusted IP addresses only. 4. Monitor network traffic: Deploy intrusion detection/prevention systems (IDS/IPS) to detect anomalous HTTP POST requests targeting /boafrm/formPortFw or unusual patterns indicative of exploitation attempts. 5. Replace legacy devices: Evaluate the use of TOTOLINK N300RH routers in critical environments and consider replacing them with more secure, enterprise-grade devices that receive regular security updates. 6. Implement strict firewall rules: Block unsolicited inbound traffic to router management interfaces from untrusted networks. 7. Conduct regular vulnerability assessments: Scan networks for presence of vulnerable TOTOLINK devices and verify firmware versions to ensure compliance with security policies. These steps go beyond generic advice by focusing on specific device controls, network architecture adjustments, and proactive monitoring tailored to the vulnerability’s characteristics.