CVE-2025-65223 is a buffer overflow vulnerability identified in the Tenda AC21 router firmware version V16.03.08.16. The vulnerability resides in the processing of the 'urls' parameter within the /goform/saveParentControlInfo HTTP endpoint. Buffer overflow (CWE-121) occurs when the input exceeds the allocated buffer size, potentially leading to memory corruption. This flaw can be triggered remotely by an attacker with access to the adjacent network segment, as the attack vector is network-based (AV:A). No privileges or authentication are required (PR:N), and no user interaction is necessary (UI:N). The vulnerability does not impact confidentiality or integrity but affects availability by causing the router to crash or reboot, resulting in denial of service. The CVSS v3.1 base score is 4.3 (medium), reflecting the limited impact and exploitation conditions. No patches or exploits are currently publicly available, but the vulnerability is published and reserved under CVE-2025-65223. The router is commonly used in home and small office environments, where disruption can affect internet connectivity and network services.

For European organizations, especially small and medium-sized businesses and residential users relying on Tenda AC21 routers, this vulnerability poses a risk of network downtime due to denial of service. While it does not compromise data confidentiality or integrity, loss of availability can disrupt business operations, remote work, and critical communications. In sectors with high dependency on continuous internet access, such as finance, healthcare, and manufacturing, even temporary outages can have operational and financial consequences. Additionally, attackers could leverage this vulnerability as part of a larger attack chain to cause disruption or as a distraction while conducting other malicious activities. The absence of known exploits reduces immediate risk, but the potential for future exploitation exists if the vulnerability is weaponized.

1. Immediately restrict access to the router’s management interface, especially the /goform/saveParentControlInfo endpoint, by implementing network segmentation and firewall rules limiting access to trusted devices only. 2. Monitor Tenda’s official channels for firmware updates addressing this vulnerability and apply patches promptly once available. 3. Employ network intrusion detection systems (NIDS) to detect anomalous HTTP requests targeting the vulnerable endpoint or unusual traffic patterns indicative of exploitation attempts. 4. For organizations with multiple Tenda AC21 devices, consider replacing affected routers with models from vendors with stronger security track records or those that provide timely security updates. 5. Educate users about the risks of exposing router management interfaces to untrusted networks, including Wi-Fi guest networks or the internet. 6. Regularly audit network devices for firmware versions and known vulnerabilities to maintain an up-to-date inventory and risk profile.