CVE-2026-2909 identifies a stack-based buffer overflow vulnerability in the Tenda HG9 router, version 300001138, specifically within the Diagnostic Ping Endpoint component accessed via the /boaform/formPing URI. The vulnerability is triggered by manipulating the pingAddr argument, which is not properly validated or bounded, allowing an attacker to overflow the stack. This overflow can corrupt memory, potentially enabling arbitrary code execution or causing a denial of service by crashing the device. The attack vector is remote network access, requiring no authentication or user interaction, making exploitation straightforward for attackers with network access to the device. The vulnerability has a CVSS 4.0 base score of 8.7, reflecting high severity due to its remote exploitability and significant impact on confidentiality, integrity, and availability. While no confirmed exploits in the wild have been reported, a public exploit is available, increasing the likelihood of exploitation attempts. The affected product, Tenda HG9, is a consumer and small business router, often deployed in home and office networks. The lack of vendor patches at the time of disclosure necessitates immediate mitigation efforts by administrators. The vulnerability’s presence in a network-facing diagnostic endpoint underscores the risk of exposure to attackers scanning for vulnerable devices. This flaw exemplifies the critical need for secure input validation in embedded device web interfaces to prevent memory corruption vulnerabilities.

The impact of CVE-2026-2909 is significant for organizations and individuals using the Tenda HG9 router. Successful exploitation can lead to full compromise of the device, allowing attackers to execute arbitrary code with elevated privileges. This can result in unauthorized access to internal networks, interception or manipulation of network traffic, and disruption of network services through denial of service conditions. For enterprises relying on these routers for perimeter or internal network connectivity, this vulnerability could serve as a foothold for lateral movement or data exfiltration. The remote and unauthenticated nature of the exploit increases the attack surface, especially in environments where these devices are exposed to the internet or untrusted networks. The availability of a public exploit further raises the risk of widespread attacks, including automated scanning and exploitation campaigns. Additionally, compromised routers can be enlisted into botnets or used to launch further attacks, amplifying the threat beyond the initial target. The vulnerability thus poses a critical risk to confidentiality, integrity, and availability of network infrastructure in affected environments.

1. Immediately restrict remote access to the Tenda HG9 router’s management and diagnostic interfaces, especially blocking access to /boaform/formPing from untrusted networks. 2. Monitor network traffic for unusual or malformed pingAddr parameter requests targeting the router’s diagnostic endpoint to detect potential exploitation attempts. 3. Apply vendor-provided patches or firmware updates as soon as they become available to address the buffer overflow vulnerability. 4. If patches are not yet available, consider replacing affected devices with alternative hardware that is not vulnerable or supports timely security updates. 5. Implement network segmentation to isolate vulnerable devices from critical infrastructure and sensitive data. 6. Employ intrusion detection/prevention systems (IDS/IPS) with signatures or heuristics capable of identifying exploitation attempts targeting this vulnerability. 7. Educate network administrators and users about the risks of exposing router management interfaces to the internet and enforce strong access controls. 8. Regularly audit and update router firmware to ensure known vulnerabilities are remediated promptly.