CVE-2026-4493 is a stack-based buffer overflow vulnerability identified in the Tenda A18 Pro router firmware version 02.03.02.28. The vulnerability resides in the function sub_423B50 within the /goform/setMacFilterCfg endpoint, which manages MAC filtering configurations. Specifically, the vulnerability is triggered by manipulating the deviceList argument, which is improperly handled, allowing an attacker to overflow the stack buffer. This overflow can corrupt adjacent memory, potentially enabling remote code execution or causing a denial of service. The attack vector is network-based and does not require authentication or user interaction, making it highly accessible to remote attackers. The vulnerability has been publicly disclosed, although no confirmed exploits in the wild have been reported yet. The CVSS 4.0 score of 8.7 reflects the ease of exploitation (network attack vector, no privileges or user interaction required) and the high impact on confidentiality, integrity, and availability. The flaw affects only the specified firmware version, and no official patches or mitigation links have been published at this time. Due to the critical nature of this vulnerability, it poses a significant risk to networks utilizing the affected Tenda A18 Pro devices, especially where these devices are exposed to untrusted networks.

The impact of CVE-2026-4493 is substantial for organizations using the Tenda A18 Pro router with the vulnerable firmware. Successful exploitation can lead to arbitrary code execution, allowing attackers to take full control of the device, manipulate network traffic, or pivot into internal networks. This compromises confidentiality by exposing sensitive data, integrity by allowing unauthorized configuration changes, and availability by potentially causing device crashes or network outages. Since the vulnerability is remotely exploitable without authentication, attackers can launch attacks from anywhere on the internet, increasing the attack surface. This can facilitate large-scale attacks such as botnet recruitment, espionage, or disruption of critical network services. Organizations relying on these routers for perimeter defense or internal segmentation face elevated risks of network compromise and data breaches. The lack of available patches further exacerbates the threat, necessitating immediate mitigation efforts.

To mitigate CVE-2026-4493, organizations should first verify if their Tenda A18 Pro devices are running the vulnerable firmware version 02.03.02.28. If so, they should immediately isolate these devices from untrusted networks to reduce exposure. Network segmentation should be enforced to limit access to the router’s management interfaces, ideally restricting them to trusted administrative networks only. Employ firewall rules to block access to the /goform/setMacFilterCfg endpoint or the device management ports from external sources. Monitor network traffic for unusual patterns indicative of exploitation attempts targeting MAC filtering configurations. Since no official patches are currently available, organizations should engage with Tenda support for firmware updates or advisories. Consider replacing vulnerable devices with models from vendors with timely security support if patching is delayed. Additionally, implement intrusion detection systems (IDS) with signatures for buffer overflow attempts targeting Tenda routers. Regularly audit router configurations and logs to detect unauthorized changes or suspicious activity.