CVE-2025-9088 is a high-severity stack-based buffer overflow vulnerability identified in the Tenda AC20 router, specifically in firmware 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 an argument list, leading to a stack-based buffer overflow condition. Because the vulnerability can be triggered remotely without requiring user interaction or authentication, an attacker can exploit this flaw over the network by sending specially crafted requests to the affected endpoint. The buffer overflow could allow an attacker to overwrite critical memory regions on the device, potentially enabling arbitrary code execution, denial of service, or system compromise. The CVSS 4.0 base score of 8.7 reflects the vulnerability's high impact on confidentiality, integrity, and availability, combined with its ease of exploitation (network vector, low attack complexity, no privileges or user interaction required). Although no known exploits are currently reported in the wild, public disclosure of the exploit code increases the risk of active exploitation. The vulnerability affects a widely deployed consumer and small office router model, which is often used as a gateway device, making it a valuable target for attackers seeking to infiltrate networks or disrupt connectivity.

For European organizations, this vulnerability poses a significant risk to network security and operational continuity. Compromise of Tenda AC20 routers could lead to unauthorized access to internal networks, interception or manipulation of sensitive data, and disruption of internet connectivity. Given that routers serve as the first line of defense and traffic control, exploitation could facilitate lateral movement within corporate or home networks, enabling further attacks such as data exfiltration or ransomware deployment. Small and medium-sized enterprises (SMEs) and home offices, which commonly use consumer-grade routers like the Tenda AC20, are particularly vulnerable due to limited IT security resources and patch management capabilities. Additionally, critical infrastructure sectors relying on such devices for connectivity could face service outages or breaches. The public availability of exploit code heightens the urgency for European organizations to address this vulnerability promptly to prevent potential targeted attacks or opportunistic exploitation by cybercriminals.

1. Immediate firmware upgrade: Organizations and users should verify if Tenda has released a patched firmware version addressing CVE-2025-9088 and apply it without delay. 2. Network segmentation: Isolate vulnerable Tenda AC20 devices from critical network segments to limit potential lateral movement in case of compromise. 3. Access control: Restrict remote management interfaces and disable unnecessary services or endpoints such as /goform/formSetVirtualSer to reduce the attack surface. 4. Intrusion detection: Deploy network monitoring and intrusion detection systems to identify anomalous traffic patterns targeting the vulnerable endpoint. 5. Vendor engagement: Engage with Tenda support channels to obtain official patches or mitigation guidance and confirm device inventory to identify all affected units. 6. Temporary workaround: If patches are unavailable, consider replacing vulnerable devices with alternative models or vendors that have addressed the vulnerability. 7. Awareness and training: Educate IT staff and end users about the risks of using outdated firmware and the importance of timely updates for network devices.