A high-severity vulnerability has been identified in certain Tenda network devices, allowing a remote, unauthenticated attacker to gain complete control over the affected product. Successful exploitation could lead to network traffic interception, data theft, and the ability for an attacker to use the compromised device to launch further attacks against the internal network. Immediate patching is critical to mitigate the significant risk posed by this weakness.

This vulnerability is a command injection flaw in the web-based management interface of the Tenda AC20 router. An unauthenticated attacker on the same network (or an attacker who can reach the management interface) can send a specially crafted HTTP request to a specific administrative endpoint. The device fails to properly sanitize user-supplied input within this request, allowing the attacker to inject and execute arbitrary operating system commands with root-level privileges, resulting in a complete compromise of the device.

This vulnerability is rated as High severity with a CVSS score of 8.8. Exploitation of this flaw could have a severe impact on business operations. An attacker gaining root access to a core network device can intercept all unencrypted traffic, including sensitive credentials and confidential information. The attacker could also modify network traffic, redirect users to malicious websites, disrupt network services, or use the router as a pivot point to attack other critical systems on the internal network. Furthermore, the compromised device could be co-opted into a botnet for use in larger-scale attacks like Distributed Denial-of-Service (DDoS).

Immediate Action: The primary remediation is to apply the security updates provided by the vendor immediately across all affected devices. Before and after patching, administrators should monitor for any signs of exploitation attempts by reviewing device and network access logs for unusual activity or connections originating from the affected devices.

Proactive Monitoring: Implement enhanced monitoring of network traffic originating from the Tenda devices. Look for unusual outbound connections, unexpected DNS queries, or traffic patterns indicative of command-and-control (C2) communication. Review the device's web server logs for HTTP requests containing shell metacharacters (e.g., ;, |, &&, $()) or other suspicious command strings.

Compensating Controls: If immediate patching is not feasible, implement the following controls to reduce the risk of exploitation:

• Disable remote/WAN management of the device's web interface.
• Restrict access to the web management interface to a limited set of trusted administrative IP addresses using firewall rules.
• Implement network segmentation to isolate the router from critical internal assets, limiting the potential impact of a compromise.

Public Exploit Available: false

Given the high CVSS score of 8.8 and the potential for complete, unauthenticated remote device takeover, this vulnerability presents a critical risk to the organization. Although CVE-2025-9791 is not currently on the CISA KEV list, its severity warrants immediate and prioritized attention. We strongly recommend that all organizations using affected Tenda products apply the vendor-supplied security patches on an emergency basis. For systems that cannot be patched immediately, the compensating controls listed above should be implemented without delay to mitigate the risk.