CVE-2025-6939 is a critical buffer overflow vulnerability identified in the TOTOLINK A3002RU router, specifically in version 3.0.0-B20230809.1615. The flaw exists within an unknown function handling HTTP POST requests to the /boafrm/formWlSiteSurvey endpoint. The vulnerability arises from improper handling of the 'submit-url' argument, which can be manipulated by an attacker to overflow a buffer. This buffer overflow can lead to arbitrary code execution or cause the device to crash, potentially resulting in denial of service. The vulnerability is remotely exploitable without requiring authentication or user interaction, increasing the risk of widespread exploitation. The CVSS v4.0 score is 8.7 (high), reflecting the ease of remote exploitation (attack vector: network), no privileges or user interaction needed, and a high impact on confidentiality, integrity, and availability. Although no public exploits are currently known to be actively used in the wild, the disclosure of the vulnerability and its exploit details increases the likelihood of future attacks. The TOTOLINK A3002RU is a consumer and small office/home office (SOHO) router, which may be deployed in various environments, including European households and small businesses. The vulnerability’s exploitation could allow attackers to gain control over the device, intercept or manipulate network traffic, or disrupt network connectivity.

For European organizations, especially small businesses and home offices relying on TOTOLINK A3002RU routers, this vulnerability poses a significant risk. Successful exploitation could lead to unauthorized access to internal networks, interception of sensitive data, or disruption of internet connectivity. This is particularly concerning for organizations handling personal data under GDPR, as breaches could lead to regulatory penalties. The compromise of network infrastructure devices like routers can also serve as a foothold for lateral movement within corporate networks, increasing the risk of more severe attacks such as ransomware or data exfiltration. Additionally, the disruption of network availability could impact business operations, customer services, and remote work capabilities, which remain critical in the European context. Given the router’s typical deployment in less-secured environments, the threat surface is broad, and the lack of authentication requirements for exploitation exacerbates the risk.

1. Immediate mitigation should include isolating affected TOTOLINK A3002RU devices from critical networks until a patch or firmware update is available. 2. Monitor network traffic for unusual POST requests targeting /boafrm/formWlSiteSurvey or anomalous behavior indicative of exploitation attempts. 3. Implement network-level protections such as web application firewalls (WAFs) or intrusion detection/prevention systems (IDS/IPS) configured to detect and block malformed HTTP POST requests to the vulnerable endpoint. 4. Encourage users to upgrade to the latest firmware version once TOTOLINK releases a patch addressing this vulnerability. 5. For organizations with multiple devices, conduct an inventory to identify all affected routers and prioritize remediation. 6. Employ network segmentation to limit the impact of compromised devices and restrict administrative access to router management interfaces. 7. Educate users on the risks of exposing router management interfaces to the internet and recommend disabling remote management if not required. 8. Regularly review and update router configurations to follow security best practices, including strong passwords and disabling unnecessary services.