Tenda F451 Router Buffer Overflow Vulnerability

A critical buffer overflow vulnerability has been identified in Tenda F451 routers running firmware version 1.0.0.7_cn_svn7958. This flaw resides within the fromGstDhcpSetSer function of the /goform/GstDhcpSetSer file, part of the httpd component. The vulnerability can be triggered remotely by manipulating the dips argument. This can allow an attacker to gain unauthorized access and control over the device. Publicly available exploits exist, increasing the risk of widespread exploitation targeting home and small business networks. This vulnerability poses a significant threat due to the potential for complete system compromise and the relative ease of exploitation.

Attack Chain

1. The attacker identifies a vulnerable Tenda F451 router running firmware version 1.0.0.7_cn_svn7958.
2. The attacker sends a specially crafted HTTP POST request to the /goform/GstDhcpSetSer endpoint.
3. This POST request contains a malicious payload within the dips argument, exceeding the buffer's intended size.
4. The fromGstDhcpSetSer function processes the request without proper bounds checking on the dips argument.
5. This causes a buffer overflow, overwriting adjacent memory regions within the httpd process.
6. The attacker carefully crafts the overflow payload to overwrite critical data, such as the return address, with the address of attacker-controlled code.
7. When the fromGstDhcpSetSer function returns, execution jumps to the attacker's code.
8. The attacker's code executes with the privileges of the httpd process, allowing for remote code execution and potential device takeover.

Impact

Successful exploitation of this buffer overflow vulnerability allows a remote attacker to execute arbitrary code on the Tenda F451 router. This can lead to complete compromise of the device, enabling the attacker to modify router settings, intercept network traffic, or use the router as a pivot point for further attacks within the network. Given the number of Tenda F451 devices deployed in homes and small businesses, this vulnerability poses a significant risk to a large number of users.

Recommendation

• Apply available patches from Tenda immediately to remediate CVE-2026-6630.
• Monitor web server logs for suspicious POST requests targeting the /goform/GstDhcpSetSer endpoint using the provided Sigma rule.
• Implement rate limiting on the /goform/GstDhcpSetSer endpoint to mitigate potential brute-force exploitation attempts.
• Consider deploying a web application firewall (WAF) with rules to detect and block common buffer overflow attack patterns.
• Enable logging for the httpd process and deploy the process creation Sigma rule to detect any spawned processes from the httpd process.