Tenda F451 Router Stack-Based Buffer Overflow Vulnerability

A critical stack-based buffer overflow vulnerability has been identified in Tenda F451 router version 1.0.0.7. The vulnerability resides within the frmL7ProtForm function of the /goform/L7Prot component, specifically within the httpd service. A remote attacker can exploit this flaw by crafting a malicious request targeting the page argument. Successful exploitation allows the attacker to execute arbitrary code on the device. Publicly available exploit code exists, increasing the risk of widespread exploitation. This vulnerability poses a significant threat to affected devices, potentially leading to full device compromise.

Attack Chain

1. Attacker identifies a vulnerable Tenda F451 router running firmware version 1.0.0.7.
2. Attacker crafts a malicious HTTP GET or POST request targeting the /goform/L7Prot endpoint.
3. The malicious request includes the page argument with a payload exceeding the buffer size allocated for it within the frmL7ProtForm function.
4. The httpd service processes the request without proper bounds checking on the page argument.
5. The oversized payload overflows the stack buffer during the execution of the frmL7ProtForm function.
6. The buffer overflow overwrites adjacent memory regions on the stack, including the return address.
7. The attacker-controlled return address redirects execution to attacker-supplied code or a return-oriented programming (ROP) chain.
8. The attacker executes arbitrary code on the router, potentially gaining full control of the device.

Impact

Successful exploitation of this vulnerability allows a remote attacker to execute arbitrary code on the affected Tenda F451 router. This can lead to a complete compromise of the device, allowing the attacker to modify router settings, intercept network traffic, or use the device as a bot in a botnet. Given the availability of public exploits, vulnerable devices are at high risk of compromise. The number of potentially affected devices is substantial, as the Tenda F451 is a widely used router model.

Recommendation

• Monitor web server logs for requests to /goform/L7Prot with unusually long page parameters, deploying the Sigma rule Detect Tenda F451 Buffer Overflow Attempt to identify potential exploitation attempts.
• Since no patch is available, consider replacing the Tenda F451 1.0.0.7 with a more secure router or firewall solution.
• Implement network segmentation to limit the impact of a compromised router on other network devices.
• Disable remote administration access to the router to reduce the attack surface.