CVE-2025-9779 is a high-severity buffer overflow vulnerability identified in the TOTOLINK A702R router, specifically affecting firmware version 4.0.0-B20211108.1423. The vulnerability resides in the function sub_4162DC within the /boafrm/formFilter component. The flaw is triggered by improper handling of the ip6addr argument, which allows an attacker to overflow a buffer remotely without requiring user interaction or prior authentication. This buffer overflow can lead to memory corruption, potentially enabling remote code execution or denial of service conditions. The vulnerability is exploitable over the network (AV:N), with low attack complexity (AC:L), no privileges required (PR:L), and no user interaction needed (UI:N). The impact on confidentiality, integrity, and availability is high, as indicated by the CVSS 4.0 score of 8.7. Although no public exploits are currently observed in the wild, a public exploit has been released, increasing the risk of exploitation. The vulnerability does not require any special conditions such as scope changes or security controls bypass, making it a straightforward target for attackers. The TOTOLINK A702R is a consumer and small office/home office (SOHO) router, and such devices are often deployed in European homes and small businesses, making this vulnerability relevant for those environments. The lack of an official patch link suggests that users and administrators need to monitor vendor advisories closely for updates or consider alternative mitigations.

For European organizations, especially small and medium enterprises (SMEs) and residential users relying on TOTOLINK A702R routers, this vulnerability poses a significant risk. Successful exploitation could allow attackers to execute arbitrary code remotely, leading to full compromise of the device. This could result in interception or manipulation of network traffic, unauthorized access to internal networks, disruption of internet connectivity, and use of the compromised device as a pivot point for further attacks. Given the high availability of these routers in home and small office environments, the vulnerability could be leveraged for large-scale botnet recruitment or targeted attacks against European entities. The impact extends to confidentiality breaches, integrity violations of network data, and availability disruptions, potentially affecting business continuity and privacy compliance obligations under regulations like GDPR.

Immediate mitigation steps include isolating the vulnerable TOTOLINK A702R devices from critical network segments and restricting remote management access to trusted IP addresses only. Network administrators should implement strict firewall rules to block unsolicited inbound traffic to the router's management interfaces. Monitoring network traffic for unusual patterns or signs of exploitation attempts is recommended. Users should regularly check the TOTOLINK official website or support channels for firmware updates addressing this vulnerability and apply patches promptly once available. If no patch is available, consider replacing the affected devices with models from vendors with timely security support. Additionally, deploying network segmentation and intrusion detection/prevention systems can help detect and contain exploitation attempts. Educating users about the risks of exposed router interfaces and encouraging strong administrative passwords will further reduce exploitation likelihood.