A critical remote code execution vulnerability in Tenda F456 routers poses a severe risk of system compromise due to a stack-based buffer overflow.

The device is vulnerable to a stack-based buffer overflow in the fromexeCommand function within the /goform/exeCommand endpoint. An authenticated attacker can trigger this memory corruption by sending a crafted cmdinput parameter, as the application fails to perform necessary length checks before copying the input into a fixed-size stack buffer.

Successful exploitation of this vulnerability allows an attacker to achieve remote code execution on the affected hardware, potentially leading to a full system takeover, unauthorized network access, or permanent denial of service. With a CVSS score of 8.8, this flaw represents a High severity risk that could disrupt critical infrastructure or expose sensitive data traversing the network, necessitating immediate attention from security teams.

Immediate Action: Since no official patch is currently available, administrators should immediately restrict access to the web management interface of the Tenda F456, ensuring it is not reachable from untrusted networks or the public internet.

Proactive Monitoring: Monitor network traffic for anomalous POST requests directed at the /goform/exeCommand endpoint and review device logs for signs of unexpected crashes or service restarts.

Compensating Controls: Deploy a Web Application Firewall (WAF) or an Intrusion Prevention System (IPS) with custom rules to inspect and drop HTTP requests containing abnormally long strings in the cmdinput parameter.

Public Exploit Available: Yes, a published proof-of-concept exists in a security research write-up hosted on GitHub.

Given the availability of a public proof-of-concept and the high severity of the potential impact, organizations utilizing Tenda F456 devices must prioritize the isolation of these units. While a vendor patch is awaited, enforcing strict network segmentation and disabling remote management access is the most effective strategy to mitigate the risk of remote exploitation. Monitor vendor communication channels closely for the release of a firmware update that addresses the memory corruption flaw.