CVE-2025-67187 is a stack-based buffer overflow vulnerability identified in the TOTOLINK A950RG router firmware version V4.1.2cu.5204_B20210112. The vulnerability resides in the setIpQosRules interface within the /lib/cste_modules/firewall.so library, specifically in the handling of the comment parameter. This parameter is not properly validated for length, allowing an attacker to supply an excessively long input that overflows the stack buffer. Stack-based buffer overflows can lead to memory corruption, enabling an attacker to execute arbitrary code with the privileges of the affected process or cause a denial of service by crashing the device. The setIpQosRules interface is likely accessible via the router’s management or configuration APIs, which may be exposed locally or remotely depending on device configuration. No authentication requirement is explicitly stated, suggesting potential for unauthenticated exploitation if the interface is reachable. No CVSS score has been assigned yet, and no patches or known exploits are currently reported. The vulnerability affects the firewall module, a critical component for network traffic management, meaning exploitation could disrupt network availability or compromise network integrity. Given the nature of the vulnerability, attackers could manipulate QoS rules to degrade service or gain persistent control over the device. TOTOLINK routers are commonly used in small office and home office environments, making these deployments particularly vulnerable. The lack of current exploit activity provides a window for proactive mitigation.

For European organizations, the impact of CVE-2025-67187 can be significant, especially for small and medium-sized enterprises (SMEs) and home office users relying on TOTOLINK A950RG routers. Successful exploitation could lead to arbitrary code execution on the router, allowing attackers to intercept, modify, or disrupt network traffic, potentially compromising confidentiality, integrity, and availability of internal communications. This could facilitate further lateral movement within corporate networks or enable persistent backdoors. Denial of service conditions could disrupt business operations reliant on internet connectivity. Given the router’s role as a network perimeter device, compromise could undermine overall network security posture. The absence of authentication requirements for exploitation increases risk, particularly if remote management interfaces are exposed. European organizations with limited IT security resources may be slower to detect or remediate such vulnerabilities, increasing exposure duration. The vulnerability also poses risks to critical infrastructure sectors that rely on stable and secure network connectivity. However, the lack of known exploits in the wild currently reduces immediate threat levels but should not lead to complacency.

1. Monitor TOTOLINK’s official channels for firmware updates addressing CVE-2025-67187 and apply patches promptly once available. 2. Restrict access to router management interfaces, especially the setIpQosRules interface, by disabling remote management or limiting access to trusted IP addresses via firewall rules. 3. Implement network segmentation to isolate vulnerable routers from critical internal systems, reducing potential lateral movement. 4. Regularly audit and monitor QoS configurations and network traffic for unusual changes or anomalies that could indicate exploitation attempts. 5. Employ intrusion detection/prevention systems (IDS/IPS) capable of detecting buffer overflow attempts or malformed QoS rule packets targeting the router. 6. Educate users and administrators about the risks of exposing router management interfaces and the importance of strong access controls. 7. Consider replacing vulnerable TOTOLINK A950RG devices with more secure alternatives if timely patching is not feasible. 8. Maintain up-to-date asset inventories to identify all affected devices within the organization for targeted remediation.