CVE-2025-11299 is a remote buffer overflow vulnerability identified in the Belkin F9K1015 router firmware version 1.00.10. The vulnerability resides in an unspecified function associated with the /goform/formWanTcpipSetup endpoint, which processes the pppUserName argument. By sending a specially crafted request with a manipulated pppUserName parameter, an attacker can overflow a buffer, potentially leading to arbitrary code execution or denial of service. The attack vector is network-based and does not require authentication or user interaction, making it highly exploitable. The vulnerability affects the router's WAN interface, allowing remote attackers to target devices exposed to the internet. Although the vendor was notified early, there has been no response or patch release. The exploit code is publicly available, increasing the risk of exploitation. The CVSS 4.0 vector indicates low attack complexity, no privileges required, no user interaction, and high impact on confidentiality, integrity, and availability. This vulnerability could allow attackers to take full control of affected devices, disrupt network connectivity, or pivot into internal networks.

For European organizations, this vulnerability poses a significant threat, especially for those deploying Belkin F9K1015 routers in environments with direct internet exposure. Successful exploitation could lead to complete compromise of the router, enabling attackers to intercept, modify, or block network traffic, disrupt business operations, or use the device as a foothold for further attacks within the corporate network. Critical infrastructure providers, SMEs, and home office setups relying on this router model could face service outages or data breaches. The lack of vendor response and patch availability increases the window of exposure. Additionally, the public availability of exploit code raises the likelihood of opportunistic attacks. Organizations in Europe with limited network segmentation or weak perimeter defenses are particularly vulnerable to remote exploitation.

Until an official patch is released, European organizations should implement the following mitigations: 1) Immediately restrict WAN interface access to the affected routers by applying firewall rules to block unsolicited inbound traffic targeting the /goform/formWanTcpipSetup endpoint or the router's management ports. 2) Employ network intrusion detection/prevention systems (IDS/IPS) with signatures or heuristics to detect and block exploit attempts against this vulnerability. 3) Segment networks to isolate affected routers from critical assets and limit lateral movement in case of compromise. 4) Monitor router logs and network traffic for unusual activity indicative of exploitation attempts. 5) Replace or upgrade affected devices where feasible, prioritizing models with active vendor support and security updates. 6) Educate IT staff about this vulnerability and ensure incident response plans include steps for potential exploitation scenarios. 7) Regularly review exposure of network devices to the internet and minimize attack surface by disabling unnecessary services or remote management features.