CVE-2025-57638 is a buffer overflow vulnerability identified in the Tenda AC9 router firmware version 1.0. The vulnerability arises from improper handling of the user-supplied 'sys.vendor' configuration parameter. Specifically, the device fails to adequately validate or sanitize the input length or content of this parameter, allowing an attacker to supply an overly long or malformed string that overflows the allocated buffer in memory. Buffer overflow vulnerabilities can lead to memory corruption, which attackers may exploit to execute arbitrary code, cause denial of service (DoS) conditions, or escalate privileges on the affected device. The Tenda AC9 is a consumer-grade wireless router commonly used in home and small office environments. Although the exact affected firmware versions are not specified beyond version 1.0, the vulnerability is confirmed as published and reserved as of August and September 2025. No CVSS score or known exploits in the wild have been reported at this time, and no patches or mitigations have been officially released. Given the nature of the vulnerability, exploitation would likely require network access to the router’s configuration interface or the ability to send crafted configuration data to the device. This vulnerability could be leveraged by attackers to compromise the router, potentially gaining control over network traffic, intercepting sensitive data, or pivoting to other devices within the network.

For European organizations, the exploitation of this vulnerability in Tenda AC9 routers could have significant security implications. Many small businesses and home offices in Europe use consumer-grade routers like the Tenda AC9 due to their affordability and ease of use. A successful exploit could allow attackers to gain unauthorized access to internal networks, intercept confidential communications, or disrupt network availability. This could lead to data breaches, loss of intellectual property, or operational downtime. Additionally, compromised routers can be used as footholds for launching further attacks within corporate networks or as part of botnets for distributed denial of service (DDoS) attacks. The impact is particularly critical for organizations that rely on these routers without additional network segmentation or security controls. Given the lack of patches and the potential for remote exploitation, the risk to confidentiality, integrity, and availability is elevated, especially in environments where these devices are exposed to untrusted networks or the internet.

To mitigate this vulnerability, European organizations should first inventory their network devices to identify any Tenda AC9 routers running vulnerable firmware versions. Immediate steps include restricting access to the router’s management interface by implementing strong access controls such as IP whitelisting, disabling remote management features, and enforcing strong authentication mechanisms. Network segmentation should be employed to isolate vulnerable devices from critical infrastructure. Monitoring network traffic for unusual activity or signs of exploitation attempts is recommended. Where possible, organizations should contact Tenda support or monitor official channels for firmware updates or patches addressing this vulnerability. In the absence of official patches, consider replacing vulnerable devices with more secure alternatives. Additionally, applying network-level protections such as intrusion detection/prevention systems (IDS/IPS) that can detect anomalous configuration attempts or buffer overflow exploit patterns can help reduce risk. Educating users about the risks of exposing router management interfaces and encouraging regular firmware updates is also advised.