CVE-2026-1689 is a remote command injection vulnerability identified in the Tenda HG10 router firmware version US_HG7_HG9_HG10re_300001138_en_xpon. The vulnerability resides in the checkUserFromLanOrWan function of the /boaform/admin/formLogin component, which processes the Host argument insecurely. An attacker can manipulate this argument to inject arbitrary system commands, which the device executes with the privileges of the web server process. The flaw does not require any authentication or user interaction, making it remotely exploitable over the network. The vulnerability stems from insufficient input validation and sanitization of the Host parameter, allowing shell metacharacters or command sequences to be injected. The CVSS 4.0 vector indicates network attack vector, low attack complexity, no privileges or user interaction required, and low impact on confidentiality, integrity, and availability, resulting in a medium severity rating of 6.9. No official patches or updates have been released by Tenda at the time of publication, but a public exploit code is available, increasing the risk of exploitation. The affected firmware version is specific to certain Tenda HG series models, including HG7, HG9, and HG10. This vulnerability could allow attackers to gain control over the device, execute arbitrary commands, potentially pivot into internal networks, disrupt services, or exfiltrate sensitive information.

The impact of CVE-2026-1689 is significant for organizations and individuals using affected Tenda HG10 routers. Successful exploitation allows remote attackers to execute arbitrary commands on the device without authentication, potentially leading to full device compromise. This can result in unauthorized access to internal networks, interception or manipulation of network traffic, installation of persistent malware, or disruption of network services. For enterprises relying on these devices for connectivity or as part of their network infrastructure, this vulnerability could serve as an entry point for lateral movement and further attacks. The medium CVSS score reflects moderate impact on confidentiality, integrity, and availability, but the ease of exploitation and lack of authentication requirements elevate the risk. The absence of patches increases exposure time, and the availability of public exploit code could lead to widespread attacks. Residential users and small businesses are particularly vulnerable due to limited security monitoring and patch management capabilities.

To mitigate CVE-2026-1689, affected organizations should immediately identify and isolate Tenda HG10 devices running the vulnerable firmware version US_HG7_HG9_HG10re_300001138_en_xpon. Network segmentation should be enforced to limit access to these devices from untrusted networks, especially the internet. Disable remote management interfaces if enabled, or restrict access to trusted IP addresses only. Employ network-level firewall rules to block unauthorized inbound traffic targeting the router's management ports. Monitor network traffic for unusual command execution patterns or unexpected outbound connections originating from the device. Since no official patches are currently available, consider deploying compensating controls such as replacing affected devices with updated models or alternative vendors that provide timely security updates. Regularly check for firmware updates from Tenda and apply them promptly once released. Additionally, implement strong network access controls and intrusion detection systems to detect and respond to exploitation attempts. Educate users about the risks and encourage reporting of suspicious device behavior.