CVE-2025-15356 is a buffer overflow vulnerability identified in the Tenda AC20 router firmware up to version 16.03.08.12. The vulnerability arises from improper handling of input parameters in the sscanf function within the /goform/PowerSaveSet endpoint. Specifically, the parameters powerSavingEn, time, powerSaveDelay, and ledCloseType can be manipulated by an unauthenticated remote attacker to cause a buffer overflow condition. This flaw allows an attacker to overwrite memory, potentially leading to arbitrary code execution with elevated privileges on the device. The vulnerability requires no user interaction and can be triggered remotely over the network, making it highly exploitable. The CVSS 4.0 base score is 8.7, reflecting the high impact on confidentiality, integrity, and availability, combined with low attack complexity and no required privileges or user interaction. While no known exploits have been observed in the wild at the time of publication, public disclosure of exploit code increases the likelihood of exploitation attempts. The affected firmware versions span from 16.03.08.0 through 16.03.08.12, covering all incremental updates in that range. The vulnerability could allow attackers to take full control of the router, disrupt network connectivity, intercept or manipulate traffic, or use the device as a foothold for further attacks within the network.

The impact of CVE-2025-15356 on organizations worldwide is significant due to the critical role routers play in network security and connectivity. Successful exploitation can lead to complete compromise of the affected Tenda AC20 devices, enabling attackers to execute arbitrary code with elevated privileges. This can result in unauthorized access to internal networks, interception and manipulation of sensitive data, disruption of network services, and potential lateral movement to other systems. Organizations relying on Tenda AC20 routers for home or small office networks may face outages or breaches. Additionally, compromised routers can be leveraged as part of botnets or for launching further attacks such as man-in-the-middle or denial-of-service attacks. The lack of authentication and user interaction requirements lowers the barrier for attackers, increasing the risk of widespread exploitation, especially in environments where firmware updates are not promptly applied. The public availability of exploit code further exacerbates the threat landscape, making timely mitigation critical.

To mitigate CVE-2025-15356, organizations should immediately verify if they are using affected versions of the Tenda AC20 firmware (16.03.08.0 through 16.03.08.12). Since no official patch links are currently provided, users should monitor Tenda’s official channels for firmware updates addressing this vulnerability and apply them as soon as they become available. In the interim, network administrators should restrict remote access to the router’s management interfaces, especially blocking access to the /goform/PowerSaveSet endpoint from untrusted networks. Implementing network segmentation to isolate vulnerable devices and deploying intrusion detection/prevention systems to monitor for exploitation attempts targeting this vulnerability can reduce risk. Disabling remote management features if not required and enforcing strong network perimeter defenses are recommended. Regularly auditing router configurations and monitoring logs for suspicious activity related to power-saving settings can help detect exploitation attempts. Finally, organizations should educate users about the importance of timely firmware updates and maintain an inventory of network devices to ensure rapid response to emerging threats.