CVE-2026-2566 identifies a stack-based buffer overflow vulnerability in the Wavlink WL-NU516U1 router firmware versions up to 130 and 260. The vulnerability resides in the /cgi-bin/adm.cgi CGI script, specifically within the sub_406194 function, which processes the firmware_url parameter. Improper validation or bounds checking of this parameter allows an attacker to overwrite the stack memory, leading to potential arbitrary code execution. The flaw can be exploited remotely over the network without requiring authentication or user interaction, making it highly dangerous. The vendor was contacted early but has not issued any patches or advisories, increasing the risk of exploitation. The vulnerability has a CVSS 4.0 score of 8.6, indicating high severity due to its remote exploitability, lack of required privileges, and significant impact on confidentiality, integrity, and availability. Although no known exploits are currently observed in the wild, the public disclosure of the exploit code increases the likelihood of active attacks. The affected device is commonly used in small to medium enterprise and home network environments, which may expose European organizations to risks of network compromise, data interception, or denial of service.

For European organizations, exploitation of CVE-2026-2566 could lead to full compromise of affected Wavlink WL-NU516U1 routers, enabling attackers to execute arbitrary code with high privileges. This can result in interception or manipulation of network traffic, unauthorized access to internal systems, disruption of network availability, and potential lateral movement within corporate networks. Critical sectors such as finance, healthcare, and government agencies relying on these devices for network connectivity could face significant operational and data security risks. The lack of vendor response and patch availability exacerbates the threat, increasing exposure time. Additionally, the remote and unauthenticated nature of the exploit lowers the barrier for attackers, including cybercriminals and state-sponsored actors targeting European infrastructure. The overall impact includes potential data breaches, service outages, and erosion of trust in network security.

Given the absence of an official patch, European organizations should implement immediate compensating controls. First, disable remote management interfaces on the Wavlink WL-NU516U1 devices to prevent external exploitation. Network segmentation should be enforced to isolate vulnerable routers from critical internal systems. Deploy intrusion detection and prevention systems (IDS/IPS) with signatures or heuristics targeting anomalous requests to /cgi-bin/adm.cgi or unusual firmware_url parameter usage. Regularly monitor network traffic for signs of exploitation attempts, including unexpected HTTP requests or buffer overflow indicators. Where possible, replace affected devices with alternative routers from vendors with active security support. Additionally, enforce strict access controls and maintain up-to-date network device inventories to quickly identify and remediate vulnerable hardware. Organizations should also engage with Wavlink for updates and monitor vulnerability databases for any forthcoming patches or advisories.