CVE-2025-67186 identifies a buffer overflow vulnerability in the TOTOLINK A950RG router firmware version 4.1.2cu.5204_B20210112, specifically in the setUrlFilterRules interface located in the /lib/cste_modules/firewall.so library. The vulnerability arises because the 'url' parameter passed to this interface is not properly validated for length, allowing an attacker to supply an overly long input string. This unchecked input leads to a buffer overflow condition, which can corrupt memory and potentially enable arbitrary code execution or cause a denial of service (DoS) by crashing the firewall module or the entire device. The vulnerability is remotely exploitable without authentication or user interaction, increasing its risk profile. Although no known exploits are currently reported in the wild, the nature of the flaw suggests that attackers could craft malicious payloads to compromise the router, gain control over network traffic, or disrupt network availability. The TOTOLINK A950RG is a consumer and small business router, and its firewall module is critical for enforcing security policies, making this vulnerability particularly impactful. The lack of a CVSS score indicates that the vulnerability is newly disclosed and pending further analysis or patching. The absence of patch links suggests that no official fix has been released yet, emphasizing the importance of interim mitigations.

For European organizations, the exploitation of CVE-2025-67186 could lead to severe consequences including unauthorized control over network traffic, interception or manipulation of data, and disruption of network services. Small and medium enterprises (SMEs) and home office environments using TOTOLINK A950RG routers are particularly vulnerable, as these devices often lack advanced security monitoring and may not be promptly updated. Compromise of these routers could serve as a foothold for attackers to pivot into internal networks, exfiltrate sensitive information, or launch further attacks such as ransomware or espionage. Critical infrastructure entities using these routers for perimeter defense could face outages or breaches, impacting service availability and data integrity. The remote and unauthenticated nature of the exploit increases the attack surface, making widespread scanning and exploitation feasible. The lack of known exploits currently provides a window for proactive defense, but the risk remains high given the potential for arbitrary code execution.

Immediate mitigation steps include isolating TOTOLINK A950RG routers from untrusted networks and restricting access to the setUrlFilterRules interface if possible. Network administrators should implement strict firewall rules to block unsolicited inbound traffic targeting the router’s management interfaces. Deploy network intrusion detection/prevention systems (IDS/IPS) with signatures or anomaly detection capable of identifying buffer overflow attempts against the firewall module. Monitor router logs for unusual activity or crashes indicative of exploitation attempts. Until an official firmware patch is released, consider replacing vulnerable devices with alternative models from vendors with timely security updates. Engage with TOTOLINK support channels to obtain information on planned patches or workarounds. Additionally, segment networks to limit the impact of a compromised router and enforce strong network access controls. Regularly audit device firmware versions and configurations to ensure compliance with security best practices.