CVE-2026-2565 is a critical security vulnerability identified in the Wavlink WL-NU516U1 wireless network adapter firmware version 20251208. The vulnerability arises from a stack-based buffer overflow in the function sub_40785C within the /cgi-bin/adm.cgi CGI script. Specifically, the flaw is triggered by improper validation and handling of the 'time_zone' parameter, which, when manipulated, causes the stack buffer to overflow. This overflow can potentially allow an attacker to overwrite the stack, leading to arbitrary code execution or system crashes. The attack vector is remote network access, meaning an attacker can exploit this vulnerability over the network without physical access or user interaction. However, exploitation complexity is high, and it requires the attacker to have high privileges on the device, which may limit the attack surface. Despite this, the availability of a public exploit increases the risk of exploitation by skilled adversaries. The vendor has not issued any patches or responded to disclosure attempts, leaving affected devices vulnerable. The vulnerability impacts confidentiality, integrity, and availability of the device and potentially the network it serves. The CVSS 4.0 score of 7.5 reflects the high severity, factoring in the remote attack vector, high complexity, and significant impact on the device's security posture.

For European organizations, this vulnerability poses a significant risk, especially for those deploying Wavlink WL-NU516U1 devices in their network infrastructure. Exploitation could lead to unauthorized remote code execution, allowing attackers to gain control over the device, intercept or manipulate network traffic, or launch further attacks within the internal network. This could compromise sensitive data confidentiality and integrity, disrupt network availability, and potentially serve as a foothold for lateral movement in corporate environments. Given the lack of vendor response and patches, affected organizations face prolonged exposure. The risk is heightened in sectors with critical infrastructure or sensitive data, such as finance, healthcare, and government agencies. Additionally, the public availability of exploits increases the likelihood of targeted attacks or opportunistic scanning by cybercriminals. The high attack complexity and requirement for high privileges somewhat mitigate the risk but do not eliminate it, especially in environments where device management is lax or default credentials are used.

European organizations should immediately inventory their network to identify any Wavlink WL-NU516U1 devices running firmware version 20251208. Since no official patch is available, organizations should consider the following mitigations: 1) Isolate affected devices on segmented network zones with strict access controls to limit exposure. 2) Restrict remote management interfaces and disable unnecessary services such as the vulnerable CGI interface if possible. 3) Enforce strong authentication and change default credentials to reduce the risk of privilege escalation. 4) Monitor network traffic for unusual activity targeting the /cgi-bin/adm.cgi endpoint or anomalous time_zone parameter usage. 5) Employ intrusion detection/prevention systems with signatures for this exploit if available. 6) Consider replacing vulnerable devices with alternative hardware from vendors with active security support. 7) Maintain up-to-date backups and incident response plans to quickly recover from potential compromises. Proactive threat hunting and user awareness about this vulnerability can further reduce risk.