CVE-2025-9088 is a high-severity stack-based buffer overflow vulnerability affecting the Tenda AC20 router, specifically version 16.03.08.12. The flaw resides in the function save_virtualser_data within the /goform/formSetVirtualSer endpoint. This function improperly handles the manipulation of its argument list, leading to a stack-based buffer overflow condition. Because the vulnerability can be triggered remotely without user interaction or prior authentication, an attacker can exploit this flaw over the network by sending specially crafted requests to the vulnerable endpoint. The buffer overflow can corrupt the stack, potentially allowing arbitrary code execution, denial of service, or system compromise. The CVSS 4.0 score of 8.7 reflects the high impact on confidentiality, integrity, and availability, combined with low attack complexity and no required privileges or user interaction. Although no public exploit is currently known to be actively used in the wild, the disclosure of the vulnerability and the availability of technical details increase the risk of exploitation. The Tenda AC20 is a consumer and small office router, and such devices are often deployed in home and small business environments, which may lack robust security controls. The vulnerability's presence in a widely used router model raises concerns about potential large-scale exploitation if attackers develop reliable exploits.

For European organizations, especially small and medium enterprises (SMEs) and home office users relying on Tenda AC20 routers, this vulnerability poses a significant risk. Successful exploitation could allow attackers to gain unauthorized control over network infrastructure, leading to interception or manipulation of network traffic, deployment of malware, or pivoting to internal networks. This could result in data breaches, disruption of business operations, and compromise of sensitive information. Given the router's role as a network gateway, exploitation could also facilitate man-in-the-middle attacks or persistent network presence. The impact is heightened in environments where patching and device management are less rigorous. Additionally, critical infrastructure or organizations with remote workforce setups using these routers may face increased exposure. The lack of known active exploits currently provides a window for mitigation, but the public disclosure means attackers may soon develop weaponized exploits.

1. Immediate mitigation should focus on upgrading the Tenda AC20 firmware to a version where this vulnerability is patched. Since no patch links are currently provided, organizations should monitor Tenda's official channels for updates. 2. In the interim, restrict remote access to the router's management interface by disabling remote administration features or limiting access to trusted IP addresses only. 3. Implement network segmentation to isolate vulnerable devices from critical systems and sensitive data. 4. Employ intrusion detection/prevention systems (IDS/IPS) with signatures or anomaly detection capabilities to identify and block exploit attempts targeting the /goform/formSetVirtualSer endpoint. 5. Regularly audit router configurations and logs for suspicious activity indicative of exploitation attempts. 6. Educate users and administrators about the risks and encourage prompt reporting of unusual network behavior. 7. Consider replacing vulnerable devices with models from vendors with stronger security track records if timely patches are unavailable.