CVE-2026-4489 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 form_fast_setting_wifi_set function within the /goform/fast_setting_wifi_set endpoint, which is responsible for handling fast Wi-Fi settings configuration. An attacker can remotely send specially crafted requests to this endpoint, causing a stack buffer overflow due to improper input validation or bounds checking. This overflow can overwrite the stack, potentially allowing arbitrary code execution or crashing the device, leading to denial of service. The vulnerability requires no user interaction and no prior authentication, making it remotely exploitable over the network. The CVSS v4.0 score is 8.7, reflecting high severity with network attack vector, low attack complexity, no privileges required, and no user interaction needed. The impact on confidentiality, integrity, and availability is high, as successful exploitation can lead to full device compromise. Although no known exploits are currently observed in the wild, a public exploit has been released, increasing the likelihood of exploitation. The lack of available patches or official mitigation details necessitates immediate defensive actions by affected users and organizations.

The vulnerability allows remote attackers to execute arbitrary code or cause denial of service on Tenda A18 Pro routers, potentially compromising the confidentiality, integrity, and availability of network traffic passing through these devices. Exploitation could lead to unauthorized access to internal networks, interception or manipulation of data, and disruption of network services. Organizations relying on these routers for critical connectivity may face network outages or breaches. The ease of exploitation without authentication or user interaction increases the risk of automated attacks and wormable scenarios. This could impact enterprise networks, ISPs, and home users alike, especially in environments where these routers are deployed as primary gateways. The public availability of an exploit further elevates the threat, potentially leading to widespread attacks if unmitigated.

1. Immediately check for firmware updates from Tenda addressing this vulnerability and apply them as soon as they become available. 2. If no patch is available, restrict access to the router’s management interfaces, especially the /goform/fast_setting_wifi_set endpoint, by implementing network segmentation and firewall rules to block unauthorized external access. 3. Disable remote management features if not required to reduce the attack surface. 4. Monitor network traffic for unusual activity targeting the vulnerable endpoint or signs of exploitation attempts. 5. Consider replacing affected devices with models from vendors with timely security update practices if patching is not feasible. 6. Employ network intrusion detection/prevention systems (IDS/IPS) with signatures for this vulnerability once available. 7. Educate network administrators about the vulnerability and ensure incident response plans include steps for dealing with exploitation attempts.