CVE-2025-6401 is a denial of service (DoS) 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, particularly within the /boafrm/formFilter endpoint. An attacker can manipulate the 'url' argument in the POST request to trigger the vulnerability. This manipulation causes the device to become unresponsive or crash, resulting in a denial of service condition. The vulnerability does not require user interaction but does require low-level privileges (PR:L) to exploit, indicating that some form of limited authentication or access to the device's management interface is necessary. The CVSS 4.0 base score is 5.1, classifying it as a medium severity issue. The attack vector is adjacent network (AV:A), meaning the attacker must be on the same local network or connected via a VPN or similar means. The vulnerability does not impact confidentiality, integrity, or availability beyond causing service disruption (VA:L). No known exploits are currently observed in the wild, but public disclosure of the exploit details increases the risk of exploitation. The lack of available patches or mitigation from the vendor at this time further elevates the risk for affected users. TOTOLINK N300RH is a consumer-grade wireless router commonly used in small office and home environments, which may be deployed in European organizations with smaller branch offices or remote setups. The vulnerability could be leveraged to disrupt network connectivity, impacting business operations reliant on this device for internet access or internal networking.

For European organizations utilizing TOTOLINK N300RH routers with the affected firmware, this vulnerability poses a risk of network disruption through denial of service attacks. The impact primarily affects availability, potentially causing temporary loss of internet connectivity or internal network access. This can hinder business operations, especially in small offices or remote locations where this router model is deployed as a primary networking device. While the vulnerability does not directly compromise data confidentiality or integrity, the resulting downtime can affect productivity and service delivery. Additionally, if attackers gain low-level access to the device, they could potentially use the DoS as a diversion for other malicious activities. The requirement for adjacent network access limits remote exploitation but does not eliminate risk, as attackers could leverage compromised internal hosts or VPN access to launch attacks. The absence of vendor patches means organizations must rely on network-level controls and monitoring to mitigate risk. Given the public disclosure of exploit details, the likelihood of opportunistic attacks may increase, especially targeting smaller organizations with less mature security postures.

1. Upgrade Firmware: Monitor TOTOLINK's official channels for firmware updates addressing this vulnerability and apply patches promptly once available. 2. Network Segmentation: Isolate management interfaces of TOTOLINK N300RH devices from general user networks to restrict access only to trusted administrators. 3. Access Controls: Enforce strong authentication mechanisms on router management interfaces and disable remote management if not required. 4. Monitoring and Logging: Implement network monitoring to detect unusual POST requests targeting /boafrm/formFilter or abnormal device behavior indicative of DoS attempts. 5. VPN and Internal Network Security: Harden VPN access and internal network security to prevent unauthorized lateral movement that could enable exploitation from adjacent networks. 6. Device Replacement: For critical environments, consider replacing affected TOTOLINK N300RH devices with models from vendors with active security support and patch management. 7. Rate Limiting: If possible, configure rate limiting on the router or upstream network devices to mitigate the impact of repeated POST requests targeting the vulnerable endpoint. 8. Incident Response Preparedness: Develop and test response plans for network outages caused by router DoS to minimize operational disruption.