CVE-2026-3975 is a stack-based buffer overflow vulnerability identified in the Tenda W3 router firmware version 1.0.0.3(2204). The vulnerability resides in the function formWifiMacFilterGet, which handles POST requests at the /goform/WifiMacFilterGet endpoint. Specifically, the issue arises from improper handling of the wl_radio parameter, allowing an attacker to manipulate this argument to overflow a stack buffer. This overflow can corrupt the stack, potentially enabling remote code execution or causing a denial of service. The vulnerability is remotely exploitable without requiring authentication or user interaction, making it highly dangerous. The exploit has been publicly released, increasing the likelihood of active exploitation. The CVSS 4.0 base score is 8.7, indicating high severity, with attack vector network (AV:N), low attack complexity (AC:L), no privileges required (PR:L), no user interaction (UI:N), and high impact on confidentiality, integrity, and availability (VC:H/VI:H/VA:H). No official patches or updates have been published yet, leaving affected devices exposed. The vulnerability affects a widely used consumer-grade router, which is often deployed in home and small office environments, potentially exposing a large number of devices to compromise. The lack of authentication requirement and ease of exploitation make this a critical concern for network security.

The impact of CVE-2026-3975 is significant for organizations and individuals using the Tenda W3 router version 1.0.0.3(2204). Successful exploitation can lead to remote code execution, allowing attackers to gain unauthorized control over the device. This can result in interception or manipulation of network traffic, deployment of malware, lateral movement within networks, or complete denial of service by crashing the device. The compromise of network infrastructure devices like routers can undermine the confidentiality, integrity, and availability of connected systems and data. For enterprises, this could mean exposure of sensitive information, disruption of business operations, and potential entry points for further attacks. The public availability of an exploit increases the risk of widespread attacks, including automated scanning and exploitation by threat actors. The vulnerability's remote and unauthenticated nature broadens the attack surface, making it a critical threat especially in environments where these routers are deployed without additional network protections.

1. Immediate mitigation should focus on isolating affected Tenda W3 devices from untrusted networks, especially the internet, to reduce exposure. 2. Disable or restrict access to the /goform/WifiMacFilterGet endpoint if possible, or apply firewall rules to block malicious POST requests targeting this function. 3. Monitor network traffic for unusual POST requests containing the wl_radio parameter to detect potential exploitation attempts. 4. Implement network segmentation to limit the impact of a compromised router on critical systems. 5. Regularly audit and inventory network devices to identify all instances of Tenda W3 routers running the vulnerable firmware. 6. Engage with Tenda support or vendor channels to obtain and apply firmware updates or patches once they become available. 7. Consider replacing vulnerable devices with models that have a stronger security track record if patches are delayed. 8. Employ intrusion detection/prevention systems (IDS/IPS) with signatures for this exploit to block or alert on attack attempts. 9. Educate network administrators about this vulnerability and ensure incident response plans include steps for router compromise scenarios. 10. Maintain up-to-date backups of router configurations to enable rapid recovery after remediation.