CVE-2025-11123 is a high-severity stack-based buffer overflow vulnerability affecting the Tenda AC18 router, specifically version 15.03.05.19. The flaw exists in an unspecified function within the /goform/saveAutoQos endpoint, where manipulation of the 'enable' argument leads to a stack-based buffer overflow condition. This vulnerability can be exploited remotely without user interaction or authentication, as indicated by the CVSS vector (AV:N/AC:L/AT:N/UI:N/PR:L). The vulnerability impacts confidentiality, integrity, and availability at a high level, allowing an attacker to potentially execute arbitrary code on the device, disrupt router functionality, or gain unauthorized access to network traffic. The exploit has been published, increasing the risk of active exploitation, although no known exploits in the wild have been reported yet. The vulnerability is critical for network security because routers like the Tenda AC18 serve as gateways for home and small office networks, and compromise can lead to widespread network infiltration or denial of service. The lack of a patch link suggests that a fix may not yet be available, emphasizing the urgency for mitigation. The vulnerability's presence in a widely deployed consumer-grade router model raises concerns about the scale of potential impact.

For European organizations, especially small and medium enterprises (SMEs) and home office users relying on Tenda AC18 routers, this vulnerability poses a significant risk. Exploitation could lead to unauthorized network access, interception of sensitive communications, and disruption of internet connectivity. Given the router's role as a network gateway, attackers could pivot to internal systems, compromising confidentiality and integrity of organizational data. The high severity and remote exploitability mean attackers can launch attacks without physical access or user interaction, increasing the threat surface. Additionally, compromised routers could be leveraged in botnets or for launching further attacks, affecting broader network stability. European organizations with limited IT security resources may be particularly vulnerable due to delayed patching or lack of awareness. The absence of a patch at the time of disclosure further exacerbates the risk, necessitating immediate mitigation efforts to prevent exploitation.

1. Immediate network segmentation: Isolate Tenda AC18 routers from critical infrastructure and sensitive systems to limit lateral movement in case of compromise. 2. Disable or restrict access to the /goform/saveAutoQos endpoint if possible, through router configuration or firewall rules, to prevent exploitation of the vulnerable function. 3. Monitor network traffic for unusual activity originating from or targeting the router, including unexpected outbound connections or spikes in traffic, which may indicate exploitation attempts. 4. Implement strict access controls on router management interfaces, including changing default credentials and limiting remote management access to trusted IPs only. 5. Regularly check for firmware updates from Tenda and apply patches promptly once available. 6. Consider replacing vulnerable Tenda AC18 devices with models from vendors with a strong security track record if patches are delayed. 7. Educate users and IT staff about the vulnerability and signs of compromise to enhance detection and response capabilities.