CVE-2025-7089 is a critical security vulnerability identified in the Belkin F9K1122 router, specifically version 1.00.33. The flaw exists in the web interface component, within the function formWanTcpipSetup, which handles WAN TCP/IP setup configurations. The vulnerability arises from improper handling of the pppUserName argument, leading to a stack-based buffer overflow. This type of vulnerability occurs when input data exceeds the allocated buffer size on the stack, overwriting adjacent memory and potentially allowing an attacker to execute arbitrary code or cause a denial of service. The vulnerability is remotely exploitable without requiring user interaction or authentication, as indicated by the CVSS vector (AV:N/AC:L/AT:N/UI:N/PR:L). The exploit targets the web management interface, which is typically accessible over the network. Although the vendor was notified early, no response or patch has been issued, and while no known exploits are currently observed in the wild, public disclosure of the exploit details increases the risk of exploitation. The CVSS 4.0 base score of 8.7 reflects the high impact on confidentiality, integrity, and availability, with low attack complexity and no user interaction needed. This vulnerability could allow attackers to gain control over affected devices, potentially leading to network compromise, interception or manipulation of traffic, or pivoting to internal networks.

For European organizations, the impact of this vulnerability could be significant, especially for enterprises and service providers relying on the Belkin F9K1122 router for WAN connectivity. Successful exploitation could lead to full compromise of the router, enabling attackers to intercept sensitive communications, disrupt network availability, or use the device as a foothold for further attacks within the corporate network. This could affect confidentiality of data, integrity of network configurations, and availability of internet services. Critical infrastructure operators, SMEs, and public sector entities using this device may face operational disruptions and data breaches. The lack of vendor response and patch availability increases the window of exposure, raising the urgency for mitigation. Additionally, the remote exploitability without authentication means attackers can target these devices over the internet or internal networks, increasing the attack surface.

Given the absence of an official patch, European organizations should implement immediate compensating controls. First, restrict access to the router's web management interface by limiting it to trusted internal networks or via VPNs, blocking WAN-side access where possible. Network segmentation should be enforced to isolate vulnerable devices from critical assets. Employ intrusion detection/prevention systems (IDS/IPS) with signatures or anomaly detection capable of identifying buffer overflow attempts targeting the formWanTcpipSetup endpoint. Regularly monitor network traffic and router logs for suspicious activity. If feasible, replace the affected Belkin F9K1122 devices with alternative models or vendors that are not vulnerable. Additionally, enforce strong network perimeter defenses and maintain up-to-date firmware on all network devices to reduce overall risk. Organizations should also prepare incident response plans specific to router compromise scenarios. Finally, maintain awareness of vendor communications for any future patches or advisories.