CVE-2024-0542 is a critical stack-based buffer overflow vulnerability identified in the Tenda W9 router, specifically in version 1.0.0.7(4456). The flaw exists in the function formWifiMacFilterGet within the httpd component of the device's firmware. This vulnerability arises from improper handling of the 'index' argument, which can be manipulated by an attacker to cause a buffer overflow on the stack. Such a condition can lead to arbitrary code execution, potentially allowing an attacker to gain control over the device remotely without requiring user interaction. The vulnerability has been publicly disclosed, and although no known exploits are currently observed in the wild, the availability of exploit details increases the risk of imminent exploitation. The vendor, Tenda, has not responded to early disclosure attempts, and no patches have been released to date. The CVSS v3.1 base score is 8.8, indicating a high severity with network attack vector, low attack complexity, requiring privileges but no user interaction, and impacting confidentiality, integrity, and availability. This vulnerability falls under CWE-121, a classic stack-based buffer overflow, which is a well-understood and dangerous class of software bugs that can lead to full system compromise.

For European organizations, the exploitation of this vulnerability could have significant consequences. Tenda W9 routers are commonly used in small to medium-sized enterprises and residential environments, often serving as gateways to corporate or home networks. Successful exploitation could allow attackers to execute arbitrary code on the router, leading to full device compromise. This could result in interception or manipulation of network traffic, disruption of internet connectivity, or the router being used as a foothold for lateral movement within internal networks. Confidential data passing through the device could be exposed or altered, and availability of network services could be disrupted, impacting business operations. Given the critical nature of the vulnerability and the lack of a vendor patch, European organizations using Tenda W9 devices are at heightened risk, especially those with limited network segmentation or monitoring capabilities.

Immediate mitigation steps should include isolating affected Tenda W9 devices from critical network segments to limit potential impact. Network administrators should implement strict access controls to restrict management interface access to trusted IP addresses only, ideally via VPN or secure management networks. Monitoring network traffic for unusual patterns or signs of exploitation attempts targeting the httpd service on these devices is essential. Since no official patch is available, organizations should consider replacing vulnerable Tenda W9 routers with devices from vendors that provide timely security updates. If replacement is not immediately feasible, disabling or restricting the vulnerable httpd component, if possible, may reduce exposure. Additionally, applying network-level protections such as intrusion prevention systems (IPS) with signatures for buffer overflow attempts targeting Tenda devices can help detect and block exploitation attempts. Regularly reviewing device firmware and vendor communications for updates is critical.