Executive brief
Multiple LB-Link router models are affected by a security flaw that allows unauthorized individuals to take full control of the device. By sending a specially crafted request to the router's web management interface, an attacker can bypass security checks and run malicious commands. This could lead to the theft of internet traffic, interception of sensitive data, or the use of the router as a foothold for further attacks on the local network.
Technical details
A command injection vulnerability exists in the /goform/set_serial_cfg interface of several LB-Link router models. The flaw is rooted in the websSecurityHandler function within the /bin/goahead binary, which incorrectly permits unauthorized access to any URL starting with the /goform/set_ prefix. Furthermore, the bs_SetSerial function in the libshare-0.0.26.so library fails to sanitize user-supplied input (such as the 'domain' field) before passing it to a system call via bl_do_system. An unauthenticated attacker on the local or adjacent network can exploit this by sending a POST request containing shell metacharacters (e.g., backticks) to execute arbitrary system commands with root privileges.
Affected products
- LB-Link BL-AC2100_AZ3 V1.0.4
- LB-Link BL-WR4000 v2.5.0
- LB-Link BL-WR9000_AE4 v2.4.9
- LB-Link BL-AC1900_AZ2 v1.0.2
- LB-Link BL-X26_AC8 v1.2.8
- LB-Link BL-LTE300_DA4 V1.2.3
Timeline
- 2025-09-22: advisory: Initial disclosure by MITRE/NVD