Executive brief
A vulnerability exists in the Tenda CX12L router, a device used to provide wireless internet connectivity. An attacker can exploit this flaw to cause the router to crash or potentially take full control of the device. This could lead to a complete loss of internet access, unauthorized monitoring of network traffic, or the use of the router as a jumping-off point to attack other devices on the home or business network.
Technical details
A stack-based buffer overflow vulnerability exists in the Tenda CX12L router (firmware version 16.03.53.12) within the 'formSetPPTPServer' function of the '/goform/SetPptpServerCfg' endpoint. The root cause is the unsafe use of the 'sscanf' function with an unbounded '%s' format specifier when parsing the 'startIp' parameter. A remote attacker can exploit this by sending a specially crafted POST request with an oversized 'startIp' value. Successful exploitation can lead to memory corruption, allowing for arbitrary code execution or a denial-of-service (DoS) condition by crashing the web server process. While some metrics suggest low privileges are required, the researcher's PoC indicates the vulnerability may be triggerable without authentication.
Affected products
- Tenda CX12L 16.03.53.12
Timeline
- 2026-04-21: disclosed: Vulnerability details and PoC published on GitHub by researcher
- 2026-05-08: advisory: CVE-2026-8138 published