CVE-2026-2567 is a stack-based buffer overflow vulnerability identified in the Wavlink WL-NU516U1 device, specifically in firmware version 20251208. The flaw exists in the function sub_401218 within the /cgi-bin/nas.cgi endpoint, which processes the User1Passwd argument. By manipulating this argument, an attacker with authenticated access can trigger a buffer overflow on the stack, potentially allowing arbitrary code execution. The vulnerability is remotely exploitable over the network without requiring user interaction, but it does require the attacker to have high-level privileges (authentication) on the device. The CVSS 4.0 score of 8.6 reflects the high impact on confidentiality, integrity, and availability, with low attack complexity and no user interaction needed. Although no active exploitation in the wild has been reported, a public exploit is available, increasing the likelihood of future attacks. This vulnerability could allow attackers to take full control of affected devices, disrupt network operations, or pivot into internal networks. The lack of an official patch link suggests that mitigation currently relies on vendor updates or workarounds. The vulnerability affects a specific firmware version, so organizations should verify their device versions and restrict access to the management interface to reduce risk.

For European organizations, the impact of CVE-2026-2567 could be significant, especially for those relying on Wavlink WL-NU516U1 devices in their network infrastructure. Exploitation could lead to full compromise of the device, enabling attackers to intercept or manipulate network traffic, disrupt services, or use the device as a foothold for further attacks within the network. This could affect confidentiality by exposing sensitive data, integrity by allowing unauthorized changes, and availability by causing device or network outages. Critical sectors such as telecommunications, government, finance, and industrial control systems could face operational disruptions or data breaches. Given the device’s role in network connectivity, exploitation could also impact supply chain security and broader organizational cybersecurity posture. The requirement for authentication reduces the attack surface but does not eliminate risk, especially if credentials are weak or compromised. The presence of a public exploit increases the urgency for mitigation to prevent targeted attacks or opportunistic exploitation.

1. Immediately verify the firmware version of all Wavlink WL-NU516U1 devices and identify those running version 20251208. 2. Apply any available firmware updates or patches from Wavlink as soon as they are released. If no patch is available, consider downgrading to a secure version or replacing affected devices. 3. Restrict access to the device management interface (/cgi-bin/nas.cgi) by implementing network segmentation, firewall rules, and VPN access to limit exposure to trusted administrators only. 4. Enforce strong authentication mechanisms, including complex passwords and multi-factor authentication, to reduce the risk of credential compromise. 5. Monitor device logs and network traffic for unusual activity indicative of exploitation attempts, such as repeated failed authentication or anomalous requests to the nas.cgi endpoint. 6. Conduct regular security audits and vulnerability scans on network devices to detect outdated firmware or misconfigurations. 7. Educate IT and security teams about this specific vulnerability and the importance of timely patching and access control. 8. Consider deploying intrusion detection/prevention systems (IDS/IPS) with signatures targeting this vulnerability’s exploit patterns. 9. Maintain an inventory of all network devices to ensure comprehensive coverage and rapid response to emerging threats.