Attack Chain

1. The attacker identifies a vulnerable LBT-T300-HW1 device with version 1.2.8 or earlier.
2. The attacker crafts a malicious HTTP request targeting the Web Management Interface.
3. The malicious request includes a payload designed to overflow the buffer when processing the vpn_pptp_server or vpn_l2tp_server arguments.
4. The crafted request is sent to the start_single_service function.
5. The start_single_service function attempts to process the overly long input without proper bounds checking.
6. The buffer overflow overwrites adjacent memory regions, including potentially executable code or critical data structures.
7. The attacker gains control of the device by redirecting execution flow to attacker-controlled code injected into the buffer.
8. The attacker executes arbitrary code on the device, potentially gaining persistent access or causing denial of service.

Impact

Successful exploitation of this vulnerability allows a remote attacker to execute arbitrary code on the affected LBT-T300-HW1 device. This could lead to complete system compromise, including data theft, modification of device settings, or use of the device as a bot in a larger attack. Given the lack of vendor response, many devices could be vulnerable if exposed to the internet.

Recommendation

• Deploy the Sigma rule Detect Suspicious VPN Server Configuration via Web Interface to detect potential exploitation attempts targeting the vulnerable start_single_service function in web server logs.
• Monitor network traffic for unusually long strings passed as values for vpn_pptp_server and vpn_l2tp_server parameters in HTTP requests to the device’s web interface.
• Apply any available patches or firmware updates released by Shenzhen Libituo Technology to address CVE-2026-7674.