CVE-2024-39769 is a classic stack-based buffer overflow vulnerability (CWE-120) found in the Wavlink AC3000 router firmware version M33A8.V5030.210505. The flaw resides in the internet.cgi script's set_qos() functionality, specifically within the cli_mac POST parameter, which does not properly validate the size of input data before copying it into a buffer. This improper input validation allows an attacker with authenticated HTTP access to send a specially crafted request that overflows the stack buffer. The overflow can overwrite critical control data such as return addresses, enabling arbitrary code execution with elevated privileges on the device. The vulnerability’s CVSS 3.1 score is 9.1 (critical), reflecting its network attack vector (AV:N), low attack complexity (AC:L), requirement for high privileges (PR:H), no user interaction (UI:N), and complete impact on confidentiality, integrity, and availability (C:H/I:H/A:H). Although no public exploits are known yet, the vulnerability’s nature and severity make it a prime candidate for exploitation once weaponized. The affected firmware version is specific, and no patch links have been provided yet, indicating that users must monitor vendor advisories closely. This vulnerability threatens the security of network infrastructure by potentially allowing attackers to gain full control over the router, disrupt network services, or intercept sensitive communications.

For European organizations, this vulnerability poses a significant risk to network security and operational continuity. Compromise of Wavlink AC3000 routers could lead to unauthorized access to internal networks, interception or manipulation of sensitive data, and disruption of critical services. Given the router’s role in managing Quality of Service (QoS), attackers could degrade network performance or cause denial of service conditions. The requirement for authentication limits exposure somewhat but does not eliminate risk, especially in environments where credential compromise or insider threats exist. The critical severity and potential for full device takeover make this a high-priority threat. Organizations relying on these devices in their network infrastructure, especially in sectors such as telecommunications, finance, government, and critical infrastructure, could face severe confidentiality breaches, data loss, and operational outages. The lack of available patches increases the urgency for interim mitigations and monitoring.

1. Immediately inventory all Wavlink AC3000 devices running the affected firmware version M33A8.V5030.210505 within the network. 2. Restrict administrative access to these devices to trusted management networks and use strong authentication mechanisms to reduce the risk of credential compromise. 3. Disable remote HTTP management interfaces or restrict them via firewall rules to prevent unauthorized access. 4. Monitor network traffic and device logs for unusual or unauthorized HTTP POST requests targeting internet.cgi endpoints. 5. Implement network segmentation to isolate vulnerable devices from critical assets. 6. Engage with Wavlink support or vendor channels to obtain firmware updates or patches as soon as they become available. 7. Consider deploying intrusion detection/prevention systems (IDS/IPS) with signatures targeting exploitation attempts of this vulnerability. 8. Educate network administrators about the risk and ensure strict password policies and multi-factor authentication are enforced. 9. If patching is delayed, consider temporary device replacement or alternative hardware for critical network segments.