A critical vulnerability has been identified in multiple Tenda networking products, including the Tenda AX3 router. This flaw, a stack-based buffer overflow, can be exploited by a remote attacker to execute arbitrary code, effectively granting them complete control over the affected device. Successful exploitation could lead to network traffic interception, data theft, or the compromise of other devices on the internal network.

The vulnerability is a stack-based buffer overflow within the formGetIptv function of the device's firmware. The function fails to properly validate the size of user-supplied input before copying it into a fixed-size stack buffer named stbpvid. An unauthenticated remote attacker can exploit this by sending a specially crafted request containing an overly long value for the associated parameter, causing the buffer to overflow. This overflow can overwrite critical data on the stack, including the function's return address, allowing the attacker to redirect the program's execution flow to malicious shellcode and achieve remote code execution with the privileges of the device's web server process.

This vulnerability is rated as critical severity with a CVSS score of 9.8. A successful exploit would result in a complete compromise of the network device, which often serves as the gateway to the internet and the primary firewall for a network segment. The business impact includes a high risk of data breaches through traffic interception (e.g., capturing credentials and sensitive information), loss of network availability, and the potential for attackers to use the compromised device as a pivot point to attack other internal systems. Furthermore, the compromised router could be conscripted into a botnet for use in larger-scale attacks against other organizations, causing significant reputational damage.

Immediate Action: Immediately apply the latest firmware updates provided by Tenda to all affected devices. After patching, it is crucial to monitor for any signs of post-remediation exploitation attempts and review device access logs for any anomalous activity that occurred prior to the update.

Proactive Monitoring: Implement network monitoring to detect suspicious traffic patterns originating from or directed to the Tenda devices. System and web server logs on the devices should be reviewed for unusually long or malformed requests, particularly those targeting IPTV-related functionalities. Configure Intrusion Detection Systems (IDS) or Intrusion Prevention Systems (IPS) with signatures to detect and block common buffer overflow attack patterns.

Compensating Controls: If patching cannot be performed immediately, implement the following controls to reduce risk:

• Ensure the device's administrative web interface is not exposed to the public internet (WAN).
• Restrict access to the administrative interface to trusted IP addresses or a dedicated management VLAN.
• Implement network segmentation to limit the potential impact of a compromised router on critical internal assets.

Public Exploit Available: false

Given the critical CVSS score of 9.8, this vulnerability represents a severe risk to the security of the network perimeter. Although it is not currently listed on the CISA KEV catalog and is not under active exploitation, the potential for complete device takeover warrants immediate action. We strongly recommend that all organizations using affected Tenda products prioritize the deployment of the vendor-supplied firmware updates to mitigate the risk of compromise.