CVE-2024-39768 is a critical security vulnerability classified under CWE-120 (Classic Buffer Overflow) affecting the Wavlink AC3000 router, specifically firmware version M33A8.V5030.210505. The flaw resides in the internet.cgi set_qos() functionality, where the cli_name POST parameter is not properly bounds-checked before copying into a stack buffer. This lack of input size validation allows an authenticated attacker to craft an HTTP POST request that overflows the buffer on the stack, potentially overwriting return addresses or other control data. Such a stack-based buffer overflow can lead to arbitrary code execution with the privileges of the web server process, which typically runs with high privileges on the device. The vulnerability requires authentication, which limits exploitation to attackers who have valid credentials or have compromised an account. However, no user interaction is needed beyond sending the malicious HTTP request. The CVSS v3.1 score of 9.1 reflects the vulnerability's network attack vector, low attack complexity, requirement for privileges, and its impact on confidentiality, integrity, and availability. Although no public exploits are currently known, the nature of the vulnerability makes it a prime candidate for exploitation once weaponized. The vulnerability affects a widely deployed consumer and SMB router model, which may be used in home offices, small businesses, and possibly some enterprise edge networks. The absence of available patches at the time of disclosure increases the urgency for mitigation measures.

For European organizations, exploitation of this vulnerability could lead to complete compromise of affected Wavlink AC3000 routers, enabling attackers to intercept, manipulate, or disrupt network traffic. This could result in data breaches, unauthorized network access, lateral movement within corporate networks, and denial of service conditions. Given the router’s role as a network gateway, attackers could establish persistent footholds or pivot to more critical internal systems. The impact is particularly severe for organizations relying on these devices in critical infrastructure sectors, small and medium enterprises, and remote office environments where alternative security controls may be limited. Confidentiality is at risk due to potential data interception; integrity is compromised by possible manipulation of network traffic or device configurations; and availability can be disrupted through device crashes or malicious payloads. The requirement for authentication reduces the attack surface but does not eliminate risk, especially if credential hygiene is poor or default passwords are in use. The lack of known exploits in the wild currently provides a window for proactive defense, but the critical severity demands immediate attention.

1. Restrict administrative access to the Wavlink AC3000 router interfaces by limiting management to trusted internal networks or VPNs. 2. Enforce strong, unique passwords and disable default or unused accounts to reduce the risk of credential compromise. 3. Monitor router logs and network traffic for unusual HTTP POST requests targeting the internet.cgi endpoint or abnormal QoS configuration changes. 4. Implement network segmentation to isolate vulnerable devices from sensitive internal resources. 5. Apply firmware updates from Wavlink as soon as they become available to address this vulnerability. 6. If immediate patching is not possible, consider deploying web application firewalls or intrusion prevention systems capable of detecting and blocking malformed HTTP requests targeting the vulnerable parameter. 7. Conduct regular vulnerability assessments and penetration tests focusing on network edge devices to identify and remediate similar risks. 8. Educate network administrators on the risks of buffer overflow vulnerabilities and the importance of timely patch management.