CVE-2024-6146 is a stack-based buffer overflow vulnerability identified in the Actiontec WCB6200Q router's HTTP server, specifically within the uh_get_postdata_withupload function. The vulnerability stems from inadequate validation of the length of user-supplied data before copying it into a fixed-size stack buffer, leading to a classic stack buffer overflow (CWE-121). This flaw can be exploited by a network-adjacent attacker who sends crafted HTTP POST requests containing oversized payloads, triggering the overflow and allowing arbitrary code execution within the context of the HTTP server process. Notably, exploitation does not require authentication or user interaction, significantly lowering the barrier for attackers. The affected firmware version is 1.2L.03.5. The vulnerability was assigned a CVSS v3.0 base score of 8.8, indicating high severity with attack vector as adjacent network, low attack complexity, no privileges required, no user interaction, and high impact on confidentiality, integrity, and availability. Although no public exploits or active exploitation have been reported, the vulnerability's nature and ease of exploitation make it a critical risk for affected deployments. The vulnerability was reported by the Zero Day Initiative (ZDI) as ZDI-CAN-21418 and published on June 18, 2024. No official patches have been linked yet, emphasizing the need for immediate mitigation strategies.

The impact of CVE-2024-6146 is severe for organizations using the Actiontec WCB6200Q router, particularly version 1.2L.03.5. Successful exploitation allows remote code execution without authentication, enabling attackers to fully compromise the device. This can lead to complete loss of confidentiality, integrity, and availability of the router and potentially the entire network segment it protects. Attackers could use the compromised router to intercept, modify, or redirect network traffic, launch further attacks within the internal network, or establish persistent backdoors. Given the router's role as a network gateway or access point, the vulnerability could facilitate lateral movement and data exfiltration, severely impacting organizational security posture. The lack of authentication and user interaction requirements increases the likelihood of automated exploitation attempts once a public exploit becomes available. The absence of patches further exacerbates the risk, making timely mitigation critical to prevent widespread compromise.

1. Immediate network segmentation: Isolate affected Actiontec WCB6200Q devices from critical network segments to limit potential attacker movement. 2. Disable or restrict HTTP management interfaces: If possible, disable the HTTP server or restrict access to trusted management networks only, reducing exposure to network-adjacent attackers. 3. Monitor network traffic for anomalous HTTP POST requests targeting the router, especially oversized payloads or unusual patterns indicative of exploitation attempts. 4. Employ intrusion detection/prevention systems (IDS/IPS) with signatures or heuristics to detect buffer overflow attempts against the HTTP server. 5. Engage with Actiontec support or vendor channels to obtain firmware updates or patches as soon as they become available; prioritize testing and deployment of these updates. 6. Consider replacing vulnerable devices with models from vendors with timely security update practices if patching is delayed. 7. Maintain up-to-date asset inventories to identify all affected devices and ensure comprehensive mitigation coverage. 8. Educate network administrators about the vulnerability and signs of exploitation to enhance incident response readiness.