Tenda F456 Router Buffer Overflow Vulnerability

A buffer overflow vulnerability has been identified in Tenda F456 router, specifically version 1.0.0.5. The vulnerability resides within the fromSafeClientFilter function located in the /goform/SafeClientFilter file. Successful exploitation allows a remote attacker to inject and execute arbitrary code. Publicly available exploit code exists, increasing the risk of widespread exploitation targeting vulnerable Tenda F456 devices. This issue poses a significant threat to network security, as a compromised router can lead to data breaches, denial of service, or further network intrusion.

Attack Chain

1. The attacker identifies a Tenda F456 router running firmware version 1.0.0.5 exposed to the internet.
2. The attacker crafts a malicious HTTP POST request targeting the /goform/SafeClientFilter endpoint.
3. The crafted request includes a specially designed payload within the menufacturer/Go argument. This payload is designed to trigger a buffer overflow in the fromSafeClientFilter function.
4. The fromSafeClientFilter function processes the malicious input without proper bounds checking.
5. The oversized payload overwrites adjacent memory regions, potentially including return addresses or other critical data.
6. When the fromSafeClientFilter function attempts to return, the overwritten return address is used, redirecting execution flow to attacker-controlled memory.
7. The attacker-controlled memory contains shellcode or other malicious instructions.
8. The router executes the attacker’s code, granting the attacker control over the device.

Impact

Successful exploitation of this vulnerability can result in complete compromise of the Tenda F456 router. An attacker can gain unauthorized access to network traffic, modify router settings, or use the compromised device as a launchpad for further attacks within the network. Given the public availability of exploit code, a large number of Tenda F456 routers could be targeted, potentially affecting numerous home and small business networks. A successful attack could lead to data theft, service disruption, and reputational damage.

Recommendation

• Apply any available patches or firmware updates released by Tenda to address CVE-2026-7033 on the F456 1.0.0.5 routers.
• Implement network intrusion detection systems (IDS) or intrusion prevention systems (IPS) rules to detect and block malicious requests targeting the /goform/SafeClientFilter endpoint.
• Deploy the Sigma rules provided below to your SIEM to detect exploitation attempts targeting the vulnerable endpoint.
• Monitor web server logs for suspicious POST requests to /goform/SafeClientFilter with abnormally large menufacturer/Go argument values.