CVE-2025-28028 is a high-severity buffer overflow vulnerability identified in several TOTOLINK router models, specifically the A830R V4.1.2cu.5182_B20201102, A950RG V4.1.2cu.5161_B20200903, A3000RU V5.9c.5185_B20201128, and A3100R V4.1.2cu.5247_B20211129. The vulnerability resides in the downloadFile.cgi component, where improper handling of the 'v5' parameter allows an attacker to overflow a buffer. This type of vulnerability (CWE-120) can lead to arbitrary code execution, denial of service, or system crashes. According to the CVSS 3.1 score of 7.3, the vulnerability is exploitable remotely over the network without requiring authentication or user interaction, increasing its risk profile. The attack vector is network-based (AV:N), with low attack complexity (AC:L), no privileges required (PR:N), and no user interaction needed (UI:N). The impact affects confidentiality, integrity, and availability, though confidentiality and integrity impacts are limited (C:L/I:L), and availability impact is also limited (A:L). No known exploits are currently reported in the wild, and no patches have been linked yet. The vulnerability affects firmware versions released between 2020 and 2021, indicating that many deployed devices may still be vulnerable if not updated or replaced. The downloadFile.cgi script is likely used for firmware or configuration file downloads, making it a critical component of the router's management interface. Exploitation could allow remote attackers to execute arbitrary code or disrupt router operations, potentially compromising network security and availability for end users and organizations relying on these devices.

For European organizations, this vulnerability poses a significant risk, especially for small and medium enterprises (SMEs) and home office environments that commonly use consumer-grade TOTOLINK routers due to their affordability and ease of deployment. Successful exploitation could lead to unauthorized access to internal networks, interception or manipulation of network traffic, and disruption of internet connectivity. This could affect business continuity, data confidentiality, and integrity of communications. Critical infrastructure entities or organizations with remote sites using these routers may experience operational disruptions. Additionally, compromised routers could be leveraged as entry points for lateral movement within corporate networks or as part of botnets for broader attacks. Given the lack of authentication and user interaction requirements, attackers can scan for vulnerable devices and exploit them en masse, increasing the scale of potential impact across Europe.

1. Immediate identification and inventory of all TOTOLINK routers in use, focusing on the affected models and firmware versions. 2. Since no official patches are currently linked, contact TOTOLINK support or monitor their official channels for firmware updates addressing this vulnerability. 3. If patches are unavailable, consider temporary mitigations such as disabling remote management interfaces or restricting access to the router management ports (e.g., blocking access to downloadFile.cgi) via firewall rules or access control lists. 4. Implement network segmentation to isolate vulnerable routers from critical network segments to limit potential lateral movement. 5. Deploy intrusion detection/prevention systems (IDS/IPS) with signatures or heuristics to detect exploitation attempts targeting downloadFile.cgi or unusual buffer overflow patterns. 6. Educate users and administrators about the risks of using outdated router firmware and encourage regular updates. 7. For high-security environments, consider replacing vulnerable devices with routers from vendors with strong security track records and timely patching practices. 8. Monitor network traffic for anomalies that could indicate exploitation attempts or successful compromises.