CVE-2025-9089 is a high-severity stack-based buffer overflow vulnerability found in the Tenda AC20 router, specifically in firmware version 16.03.08.12. The vulnerability resides in the function sub_48E628 within the /goform/SetIpMacBind endpoint. This function improperly handles its argument list, allowing an attacker to overflow the stack buffer by sending a specially crafted request remotely. Because the vulnerability is remotely exploitable without user interaction and requires only low privileges (PR:L), it poses a significant risk. Exploiting this flaw could allow an attacker to execute arbitrary code on the device, potentially leading to full compromise of the router. This could enable attackers to manipulate network traffic, intercept sensitive data, or pivot into internal networks. Although no known exploits are currently observed in the wild, the public disclosure of the exploit code increases the likelihood of exploitation attempts. The CVSS 4.0 base score of 8.7 reflects the high impact on confidentiality, integrity, and availability, combined with ease of exploitation and no user interaction required. The vulnerability does not require special privileges beyond low-level access, and the attack surface is broad due to the network-facing nature of the vulnerable endpoint. No official patches or mitigations have been linked yet, which increases the urgency for affected users to implement compensating controls or upgrade firmware once available.

For European organizations, this vulnerability poses a critical risk to network infrastructure security. Tenda AC20 routers are commonly used in small to medium enterprises and home office environments, which are integral to business operations. Successful exploitation could lead to unauthorized access to internal networks, interception of confidential communications, and disruption of network availability. This is particularly concerning for sectors handling sensitive personal data under GDPR, such as healthcare, finance, and public administration. Compromise of network devices could also facilitate lateral movement by attackers, leading to broader organizational breaches. Given the remote exploitability and lack of user interaction, attackers can target vulnerable routers en masse, potentially causing widespread service disruptions or data breaches. The vulnerability could also be leveraged in botnet creation or DDoS attacks, affecting service reliability. European organizations relying on Tenda AC20 devices should consider this vulnerability a high priority threat to their network security posture.

Since no official patches are currently available, European organizations should immediately implement the following mitigations: 1) Isolate Tenda AC20 devices from direct internet exposure by placing them behind firewalls or VPNs to restrict access to the /goform/SetIpMacBind endpoint. 2) Disable or restrict remote management interfaces on the router to trusted IP addresses only. 3) Monitor network traffic for unusual requests targeting the vulnerable endpoint, employing intrusion detection systems with custom signatures for this exploit. 4) Replace affected Tenda AC20 routers with alternative devices from vendors with timely security updates if feasible. 5) Regularly check for firmware updates from Tenda and apply patches promptly once released. 6) Employ network segmentation to limit the impact of a compromised router on critical systems. 7) Educate IT staff about this vulnerability and ensure incident response plans include steps for router compromise scenarios. These targeted actions go beyond generic advice by focusing on access control, monitoring, and network architecture adjustments specific to this vulnerability.