CVE-2025-15356 is a remote buffer overflow vulnerability identified in the Tenda AC20 router firmware versions up to 16.03.08.12. The vulnerability exists in the sscanf function used in the /goform/PowerSaveSet endpoint, which processes parameters including powerSavingEn, time, powerSaveDelay, and ledCloseType. Improper validation and handling of these input arguments lead to a buffer overflow condition, which can be triggered remotely without requiring authentication or user interaction. This flaw allows an attacker to overwrite memory, potentially leading to arbitrary code execution with elevated privileges on the device. The vulnerability has a CVSS 4.0 base score of 8.7, indicating high severity, with network attack vector, low attack complexity, no privileges or user interaction required, and high impact on confidentiality, integrity, and availability. Although no exploits have been observed in the wild yet, the public disclosure of the exploit details increases the likelihood of exploitation attempts. The affected device, Tenda AC20, is a widely used consumer and small business router, often deployed in home and office environments, making it a critical point of network security. Successful exploitation could allow attackers to compromise the router, intercept or manipulate network traffic, pivot to internal networks, or disrupt network availability. The vulnerability underscores the importance of secure input validation in embedded device firmware and the risks posed by exposed management interfaces.

For European organizations, exploitation of this vulnerability could lead to severe consequences including unauthorized access to internal networks, interception of sensitive communications, and disruption of network services. Given that Tenda AC20 routers are commonly used in small to medium enterprises and residential settings, attackers could leverage compromised devices as footholds for broader network intrusion or as part of botnets for distributed attacks. The confidentiality of corporate and personal data transmitted through these routers could be compromised, and integrity of network traffic could be undermined. Availability risks include potential denial of service or device bricking. The lack of authentication and user interaction requirements lowers the barrier for attackers, increasing the risk profile. Organizations relying on these devices for critical connectivity or remote access may face operational disruptions and reputational damage. The threat is particularly acute for sectors with high reliance on secure network infrastructure such as finance, healthcare, and government services within Europe.

1. Immediate identification and inventory of all Tenda AC20 devices within the network environment. 2. Monitor Tenda’s official channels for firmware updates addressing CVE-2025-15356 and apply patches promptly upon release. 3. Until patches are available, restrict remote access to router management interfaces by implementing network segmentation and firewall rules limiting access to trusted IP addresses only. 4. Disable remote management features if not strictly necessary to reduce attack surface. 5. Employ network intrusion detection systems (NIDS) to monitor for anomalous traffic patterns or exploit attempts targeting the /goform/PowerSaveSet endpoint. 6. Conduct regular security audits and penetration testing focusing on router and IoT device security. 7. Educate users and administrators about the risks of unpatched router firmware and encourage timely updates. 8. Consider replacing vulnerable devices with models from vendors with stronger security track records if patching is delayed or unsupported. 9. Implement network-level encryption and VPNs to protect sensitive data in transit, mitigating risks from compromised routers. 10. Maintain robust incident response plans to quickly isolate and remediate affected devices in case of compromise.