CVE-2025-11120 identifies a critical buffer overflow vulnerability in the Tenda AC8 router firmware version 16.03.34.06. The vulnerability resides in the formSetServerConfig function, which processes requests to the /goform/SetServerConfig endpoint. Improper input validation or bounds checking in this function allows an attacker to send specially crafted requests that overflow a buffer, potentially overwriting adjacent memory. This can lead to arbitrary code execution or cause the device to crash, resulting in denial of service. The attack vector is remote network access, requiring no authentication or user interaction, making exploitation straightforward for attackers with network access to the device. The vulnerability has a CVSS 4.0 score of 8.7, indicating high severity due to its impact on confidentiality, integrity, and availability, combined with low attack complexity and no required privileges. Although no active exploitation has been reported, the availability of a public exploit increases the likelihood of future attacks. The lack of an official patch at the time of disclosure necessitates immediate risk mitigation. This vulnerability is particularly concerning for environments where Tenda AC8 routers are deployed with management interfaces exposed to untrusted networks or the internet, as attackers can leverage this flaw to gain control over network infrastructure or disrupt services.

For European organizations, exploitation of this vulnerability could lead to severe consequences including unauthorized access to internal networks, interception or manipulation of sensitive data, and disruption of network availability. Critical infrastructure, small and medium enterprises, and residential users relying on Tenda AC8 routers may experience network outages or compromise of connected systems. The ability to execute arbitrary code remotely without authentication poses a significant risk of lateral movement within corporate networks, potentially facilitating further attacks such as data exfiltration or ransomware deployment. Additionally, compromised routers could be used as part of botnets for distributed denial-of-service (DDoS) attacks, impacting broader internet stability. The impact is exacerbated in organizations lacking network segmentation or those with exposed router management interfaces. Given the high CVSS score and public exploit availability, the threat level is elevated, demanding urgent attention from affected entities.

1. Immediately monitor for firmware updates from Tenda addressing CVE-2025-11120 and apply patches as soon as they become available. 2. Until patches are released, restrict access to the router’s management interface by implementing firewall rules that limit access to trusted IP addresses only. 3. Disable remote management features on the Tenda AC8 routers if not strictly necessary. 4. Employ network segmentation to isolate router management interfaces from general user networks and the internet. 5. Conduct network traffic monitoring to detect anomalous requests targeting /goform/SetServerConfig or unusual buffer overflow indicators. 6. Educate IT staff and users about the risks and signs of router compromise. 7. Consider replacing vulnerable devices with models from vendors with stronger security track records if patching is delayed. 8. Implement intrusion detection/prevention systems (IDS/IPS) with signatures for this vulnerability once available. 9. Regularly audit router configurations and firmware versions across the organization to ensure compliance and timely updates.