CVE-2025-57071 is a high-severity vulnerability identified in the Tenda G3 router firmware version 3.0br_V15.11.0.17. The flaw is a stack-based buffer overflow located in the vpnUsers parameter within the formAddVpnUsers function. This vulnerability arises when the device processes a specially crafted request targeting this parameter, leading to memory corruption on the stack. Exploitation of this vulnerability does not require authentication or user interaction, and can be triggered remotely over the network. The primary consequence of successful exploitation is a Denial of Service (DoS) condition, where the router crashes or becomes unresponsive, disrupting network connectivity. The vulnerability is classified under CWE-121 (Stack-based Buffer Overflow), indicating improper bounds checking on input data. The CVSS v3.1 base score is 7.5, reflecting high severity due to the network attack vector, low attack complexity, no privileges required, and no user interaction needed. Although no known exploits are currently reported in the wild and no patches have been published yet, the presence of this vulnerability in a widely deployed consumer router model poses a significant risk. Attackers could leverage this flaw to disrupt home or small office networks by remotely crashing the device, potentially causing extended downtime and impacting dependent services.

For European organizations, especially small and medium enterprises (SMEs) and home offices relying on Tenda G3 routers, this vulnerability could lead to significant operational disruptions. The DoS condition would interrupt internet connectivity and VPN services, potentially halting business communications and remote access capabilities. This is particularly critical for organizations that depend on VPN tunnels for secure remote work, a common practice in Europe. While the vulnerability does not directly compromise confidentiality or integrity, the loss of availability can degrade productivity and may indirectly affect business continuity. Additionally, repeated exploitation attempts could increase network instability and complicate incident response. Given the lack of authentication requirements, attackers can exploit this vulnerability from anywhere on the internet, increasing the threat surface. European organizations with limited IT security resources may face challenges in detecting and mitigating such attacks promptly, exacerbating the impact.

Organizations should immediately inventory their network devices to identify any Tenda G3 routers running the vulnerable firmware version 3.0br_V15.11.0.17. Until an official patch is released, it is advisable to restrict remote access to the router’s management interfaces by implementing network-level controls such as firewall rules or VPN gateways that limit access to trusted IP addresses. Disabling remote management features, if enabled, can reduce exposure. Network administrators should monitor router logs and network traffic for unusual or malformed requests targeting the vpnUsers parameter. Employing intrusion detection/prevention systems (IDS/IPS) with custom signatures to detect attempts to exploit this buffer overflow can provide additional protection. Organizations should also plan to update the router firmware promptly once a vendor patch becomes available. As a longer-term measure, consider replacing vulnerable devices with models that receive regular security updates and have a proven security track record. Educating users about the risks of exposing router management interfaces to the internet is also critical.