CVE-2024-39803

Multiple buffer overflow vulnerabilities, including one in the `sel_mode` POST parameter, exist in the `qos.cgi` `qos_settings()` functionality of the Wavlink AC3000 router running firmware version M33A8.V5030.210505. These flaws allow a specially crafted HTTP request to trigger a stack-based buffer overflow, classified under CWE-120. The vulnerability carries a CVSS v3.1 base score of 9.1 (AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H), indicating critical severity due to its potential for high-impact exploitation across confidentiality, integrity, and availability.

An attacker with high-privilege authenticated access (PR:H) can exploit these vulnerabilities remotely over the network (AV:N) with low complexity (AC:L). By sending a malicious HTTP request to the affected `qos.cgi` endpoint, the attacker triggers the stack-based buffer overflow in `qos_settings()`, potentially leading to arbitrary code execution, full system compromise, or denial of service, with scope expanded to changed components (S:C).

Mitigation details are outlined in the Talos Intelligence advisory (TALOS-2024-2049), available at https://talosintelligence.com/vulnerability_reports/TALOS-2024-2049. Security practitioners should consult this report for vendor-specific patch information or workarounds, such as restricting access to the `qos.cgi` endpoint or upgrading firmware if available.