CVE-2025-4809 is a critical security vulnerability identified in the Tenda AC7 router firmware version 15.03.06.44. The flaw exists in the function fromSafeSetMacFilter within the /goform/setMacFilterCfg endpoint. Specifically, the vulnerability arises from improper handling of the deviceList argument, which leads to a stack-based buffer overflow. This type of vulnerability occurs when data exceeding the buffer's capacity is written to the stack, potentially overwriting adjacent memory and enabling arbitrary code execution or system crashes. The vulnerability is remotely exploitable without requiring user interaction or prior authentication, as indicated by the CVSS vector (AV:N/AC:L/AT:N/UI:N/PR:L). The CVSS score of 8.7 (high severity) reflects the significant risk posed by this flaw, especially given the high impact on confidentiality, integrity, and availability (VC:H/VI:H/VA:H). Although no known exploits are currently reported in the wild, the public disclosure of the exploit code increases the likelihood of active exploitation attempts. Attackers could leverage this vulnerability to execute arbitrary code on the router, potentially gaining control over the device, intercepting or manipulating network traffic, or launching further attacks within the network. The vulnerability's presence in a widely deployed consumer and small business router model makes it a critical concern for network security.

For European organizations, this vulnerability poses a substantial risk to network infrastructure security. The Tenda AC7 router is commonly used in small to medium enterprises and residential environments, which often serve as entry points to corporate networks or remote work setups. Exploitation could lead to unauthorized access to internal networks, data interception, or disruption of network services, impacting confidentiality, integrity, and availability of organizational data and communications. Given the remote exploitability without authentication, attackers could compromise devices en masse, leading to potential large-scale network outages or data breaches. This is particularly concerning for sectors with stringent data protection requirements under GDPR, where unauthorized data exposure could result in regulatory penalties. Additionally, compromised routers could be used as launchpads for lateral movement or as part of botnets, amplifying the threat landscape for European entities.

To mitigate this vulnerability, European organizations should immediately identify and inventory all Tenda AC7 routers running firmware version 15.03.06.44. Although no official patch links are currently provided, organizations should monitor Tenda's official channels for firmware updates addressing this issue and apply them promptly once available. In the interim, network administrators should restrict remote access to router management interfaces, ideally limiting access to trusted IP addresses or internal networks only. Implementing network segmentation can reduce the risk of lateral movement if a device is compromised. Employing intrusion detection and prevention systems (IDS/IPS) with signatures tuned to detect exploitation attempts targeting /goform/setMacFilterCfg can provide early warning and block attacks. Additionally, organizations should enforce strict monitoring of router logs for anomalous activity and consider replacing vulnerable devices if timely patches are unavailable. User education on the risks of exposed management interfaces and regular security audits of network devices will further strengthen defenses.