CVE-2025-6302 is a critical security vulnerability identified in the TOTOLINK EX1200T router, specifically version 4.1.2cu.5232_B20210713. The flaw exists in the setStaticDhcpConfig function within the /cgi-bin/cstecgi.cgi file. This function improperly handles the 'Comment' argument, which can be manipulated by an attacker to trigger a stack-based buffer overflow. Such a vulnerability allows an attacker to overwrite the stack memory, potentially leading to arbitrary code execution, denial of service, or system compromise. The vulnerability is remotely exploitable without requiring user interaction or prior authentication, as indicated by the CVSS vector (AV:N/AC:L/AT:N/UI:N/PR:L). The CVSS 4.0 base score is 8.7, categorizing it as a high-severity issue. The exploit has been publicly disclosed, increasing the risk of exploitation, although no confirmed exploits in the wild have been reported to date. The vulnerability impacts the confidentiality, integrity, and availability of the affected device, as successful exploitation could allow attackers to execute arbitrary commands or disrupt network operations. The TOTOLINK EX1200T is a consumer and small office/home office (SOHO) router, which may be deployed in various environments including enterprise branch offices and residential settings. The vulnerability resides in a CGI script, which is typically accessible via the device’s web management interface, making remote exploitation feasible over the network. Given the nature of the buffer overflow, exploitation could lead to full device compromise, enabling attackers to pivot into internal networks or intercept sensitive data traffic routed through the device.

For European organizations, this vulnerability poses a significant risk, especially for small and medium-sized enterprises (SMEs) and home office setups that rely on TOTOLINK EX1200T routers for network connectivity. Exploitation could result in unauthorized access to internal networks, interception of sensitive communications, and disruption of business operations due to device crashes or reboots. Critical infrastructure operators or organizations with remote branch offices using these routers may face increased exposure to cyber espionage or ransomware attacks if attackers leverage this vulnerability as an initial foothold. The lack of authentication requirement and remote exploitability increases the attack surface, potentially allowing widespread scanning and exploitation attempts. Additionally, the public disclosure of the exploit code may accelerate attack campaigns targeting vulnerable devices in Europe. The impact extends beyond confidentiality to integrity and availability, as attackers could modify network configurations or cause denial of service, affecting business continuity and trust in network security.

Immediately verify if TOTOLINK EX1200T devices running version 4.1.2cu.5232_B20210713 are deployed within the organization’s network, including branch offices and remote sites. Isolate affected devices from untrusted networks until patched or mitigated to reduce exposure to remote attacks. Monitor network traffic for unusual access patterns to the /cgi-bin/cstecgi.cgi endpoint, especially POST requests manipulating DHCP configurations. Implement network-level access controls restricting management interface access to trusted IP addresses or VPN-only access to prevent unauthorized remote exploitation. Engage with TOTOLINK support or official channels to obtain and apply firmware updates or patches addressing this vulnerability as soon as they become available. If immediate patching is not possible, consider disabling the web management interface or restricting it to local access only to mitigate remote exploitation risk. Deploy intrusion detection/prevention systems (IDS/IPS) with signatures or heuristics capable of detecting buffer overflow attempts targeting the affected CGI script. Conduct regular vulnerability scans and penetration tests focusing on network devices to identify and remediate similar vulnerabilities proactively. Educate IT staff on the risks associated with outdated router firmware and the importance of timely updates and configuration hardening.