CVE-2026-4490 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 setSchedWifi function, which is accessible via the /goform/openSchedWifi endpoint. This function improperly handles input data, leading to a stack-based buffer overflow condition. Because the vulnerability is remotely exploitable without requiring authentication or user interaction, an attacker can send specially crafted requests to the vulnerable endpoint to overwrite the stack memory. This can result in arbitrary code execution with the privileges of the affected process, typically root or system-level on the router. The CVSS 4.0 base score of 8.7 reflects the high impact on confidentiality, integrity, and availability, combined with the ease of remote exploitation. Although no active exploitation has been reported in the wild, the public availability of an exploit increases the likelihood of attacks. The vulnerability affects only the specified firmware version, and no official patches have been linked yet. The flaw could be leveraged to disrupt network services, intercept or manipulate traffic, or pivot into internal networks, posing a significant threat to organizations relying on this router model.

The impact of CVE-2026-4490 is substantial for organizations using the Tenda A18 Pro router with the vulnerable firmware. Successful exploitation can lead to full device compromise, allowing attackers to execute arbitrary code, disrupt network operations, and potentially intercept or manipulate sensitive data passing through the router. This compromises the confidentiality, integrity, and availability of network communications. Given the router's role as a gateway device, attackers could use it as a foothold for lateral movement within corporate or home networks, escalating the scope of the breach. The lack of authentication and user interaction requirements lowers the barrier for attackers, increasing the risk of automated or mass exploitation campaigns. Organizations in sectors with critical infrastructure or sensitive data are particularly vulnerable to operational disruptions and data breaches resulting from this flaw.

To mitigate CVE-2026-4490, organizations should immediately verify if their Tenda A18 Pro routers are running the affected firmware version 02.03.02.28. If so, they should seek firmware updates or patches from Tenda as a priority. In the absence of official patches, network administrators should restrict access to the router's management interfaces, especially the /goform/openSchedWifi endpoint, by implementing network segmentation and firewall rules to block remote access from untrusted networks. Disabling remote management features or restricting them to trusted IP addresses can reduce exposure. Monitoring network traffic for unusual requests targeting the vulnerable endpoint can help detect exploitation attempts. Additionally, organizations should consider replacing affected devices with models from vendors with more robust security update practices if patches are delayed. Regularly auditing and updating router firmware as part of asset management is critical to prevent similar vulnerabilities.