CVE-2025-7087 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 formL2TPSetup located at /goform/formL2TPSetup. The vulnerability arises from improper handling of the L2TPUserName argument, which leads to a stack-based buffer overflow. This type of overflow occurs when more data is written to a buffer located on the stack than it can hold, potentially overwriting adjacent memory and allowing an attacker to execute arbitrary code or cause a denial of service. The vulnerability is remotely exploitable without requiring user interaction or prior authentication, making it highly dangerous. The CVSS 4.0 score of 8.7 (high severity) reflects the ease of exploitation (network attack vector, low attack complexity, no privileges or user interaction required) and the significant impact on confidentiality, integrity, and availability. The vendor, Belkin, was notified early but has not responded or provided a patch, and a public exploit has been disclosed, increasing the risk of active exploitation. This vulnerability targets the L2TP VPN setup functionality, which is often used in enterprise and home networks for secure remote access, thus compromising this component can lead to full device compromise or network infiltration.

For European organizations, this vulnerability poses a significant risk, especially for those relying on Belkin F9K1122 routers in their network infrastructure. Exploitation can lead to unauthorized remote code execution, enabling attackers to take full control of the affected device. This can result in interception or manipulation of network traffic, lateral movement within corporate networks, data exfiltration, or disruption of network services. Given the critical nature of the flaw and the lack of vendor response, organizations face increased exposure to targeted attacks or opportunistic exploitation by cybercriminals. Small and medium enterprises (SMEs) and home office setups using this router model are particularly vulnerable, as they may lack advanced security monitoring. The compromise of VPN setup functions undermines secure remote access, which is crucial for European businesses with remote workforces. Additionally, the potential for denial of service could disrupt business continuity and critical communications.

Immediate mitigation steps include isolating or segmenting affected Belkin F9K1122 devices from critical network segments to limit potential damage. Organizations should disable L2TP VPN functionality on these routers if not in use or until a patch is available. Network administrators should monitor network traffic for unusual activity originating from or targeting these devices, including attempts to access /goform/formL2TPSetup endpoints. Employing intrusion detection/prevention systems (IDS/IPS) with signatures for known exploits targeting this vulnerability can help detect and block attacks. Where possible, replace affected routers with models from vendors that provide timely security updates. Additionally, enforcing strict network access controls and using VPN alternatives with stronger security postures can reduce risk. Organizations should maintain up-to-date asset inventories to identify and remediate vulnerable devices promptly. Finally, engaging with Belkin support channels to demand a security patch and monitoring vulnerability databases for updates is recommended.