Executive brief
A security vulnerability exists in the Tenda CX12L router, a device used to provide Wi-Fi and networking for homes and small offices. An attacker can exploit this flaw to crash the router's management interface or potentially take full control of the device. This could lead to a total loss of internet connectivity or allow an unauthorized user to monitor network traffic and access sensitive data.
Technical details
A stack-based buffer overflow vulnerability exists in the 'form_fast_setting_wifi_set' function within the '/goform/fast_setting_wifi_set' endpoint of Tenda CX12L firmware (v16.03.53.12). The root cause is the unsafe use of the 'sprintf' function when processing the user-controlled 'ssid' parameter. Specifically, when the device generates a 5GHz SSID, it appends '_5G' to the input and copies it into a fixed 64-byte stack buffer without length validation. An attacker with network access and low-level privileges can provide an overly long SSID string to overwrite the stack, including the saved frame pointer and return address, enabling arbitrary code execution or a crash of the 'httpd' process. A public exploit has been disclosed.
Affected products
- Tenda CX12L 16.03.53.12
Timeline
- 2026-05-22: disclosed: Vulnerability details and PoC published on GitHub
- 2026-06-08: advisory: CVE-2026-11503 published