CVE-2025-5795 is a critical buffer overflow vulnerability identified in the Tenda AC5 router, specifically affecting firmware versions 1.0 and 15.03.06.47. The vulnerability resides in the function 'fromadvsetlanip' within the '/goform/AdvSetLanip' endpoint. The issue arises due to improper handling of the 'lanMask' argument, which can be manipulated by an attacker to overflow a buffer. This overflow can lead to arbitrary code execution or cause the device to crash, resulting in denial of service. The vulnerability is remotely exploitable without requiring user interaction or authentication, making it highly dangerous. The CVSS 4.0 base score is 8.7, indicating a high severity level, with attack vector network (AV:N), low attack complexity (AC:L), no privileges required (PR:L), no user interaction (UI:N), and high impact on confidentiality, integrity, and availability (VC:H, VI:H, VA:H). Although no known exploits are currently observed in the wild, a public exploit has been disclosed, increasing the risk of exploitation. The vulnerability's presence in a widely deployed consumer-grade router means that attackers could leverage it to gain control over the device, intercept or manipulate network traffic, or pivot into internal networks, potentially compromising connected systems and data.

For European organizations, this vulnerability poses a significant risk, especially for small and medium enterprises (SMEs) and home office environments that commonly use consumer-grade routers like the Tenda AC5. Exploitation could lead to unauthorized access to internal networks, data interception, and disruption of network services. Critical infrastructure or organizations relying on these routers for network connectivity could face operational disruptions or data breaches. The remote and unauthenticated nature of the exploit means attackers can target vulnerable devices en masse, potentially leading to widespread compromise. Additionally, given the router's role at the network perimeter, successful exploitation could facilitate lateral movement within corporate networks, threatening confidentiality and integrity of sensitive information. The lack of patches or official updates at the time of disclosure exacerbates the risk, requiring organizations to implement compensating controls promptly.

1. Immediate network segmentation: Isolate Tenda AC5 routers from critical network segments to limit potential lateral movement if compromised. 2. Disable remote management interfaces or restrict access to trusted IP addresses only, reducing exposure to remote exploitation. 3. Monitor network traffic for unusual activity originating from or targeting the router, including unexpected outbound connections or anomalous LAN traffic. 4. Employ intrusion detection/prevention systems (IDS/IPS) with signatures or heuristics capable of detecting exploitation attempts targeting this vulnerability. 5. Where possible, replace Tenda AC5 devices with routers from vendors with timely security update practices, especially in sensitive environments. 6. Regularly check for firmware updates from Tenda addressing this vulnerability and apply patches as soon as they become available. 7. Educate IT staff and users about the risks and signs of router compromise to enable rapid detection and response. 8. Implement network-level access controls and strong authentication mechanisms for router management interfaces to prevent unauthorized access.