CVE-2023-26801: Lb-link Bl-lte300 Firmware RCE Vulnerability

CVE-2023-26801 Overview

CVE-2023-26801 is a command injection vulnerability affecting multiple LB-LINK wireless router models. The vulnerability exists in the /goform/set_LimitClient_cfg endpoint, where the mac, time1, and time2 parameters fail to properly sanitize user-supplied input before being passed to system commands. This allows unauthenticated remote attackers to execute arbitrary commands on the affected devices with root privileges.

Critical Impact

This vulnerability enables unauthenticated remote code execution on affected LB-LINK routers. Attackers can gain complete control over network infrastructure, intercept traffic, or use compromised devices as part of botnet operations. According to Akamai's security research, this vulnerability has been actively exploited to spread Mirai botnet variants.

Affected Products

• LB-LINK BL-AC1900_2.0 Firmware v1.0.1
• LB-LINK BL-WR9000 Firmware v2.4.9
• LB-LINK BL-X26 Firmware v1.2.5
• LB-LINK BL-LTE300 Firmware v1.0.8

Discovery Timeline

• 2023-03-26 - CVE-2023-26801 published to NVD
• 2025-05-05 - Last updated in NVD database

Technical Details for CVE-2023-26801

Vulnerability Analysis

This command injection vulnerability (CWE-77) stems from improper handling of user-controlled input within the router's web management interface. The affected endpoint /goform/set_LimitClient_cfg processes parameters intended for client limitation configuration without adequate input validation or sanitization.

When processing requests to this endpoint, the firmware directly incorporates the mac, time1, and time2 parameter values into shell commands executed on the underlying Linux-based operating system. An attacker can craft malicious input containing shell metacharacters and command sequences that will be interpreted and executed by the system shell.

The vulnerability requires no authentication, meaning any attacker with network access to the router's web interface can exploit it. Given the typical deployment of these devices on network perimeters, successful exploitation grants attackers a foothold for lateral movement, traffic interception, or incorporation into botnet infrastructure.

Root Cause

The root cause of this vulnerability is insufficient input validation in the firmware's web application handler. The mac, time1, and time2 parameters are passed directly to system shell commands without proper sanitization or escaping of shell metacharacters. This allows attackers to inject arbitrary commands by including special characters such as semicolons (;), pipes (|), or command substitution sequences in their input.

Attack Vector

The attack vector is network-based and requires no authentication or user interaction. An attacker can send a specially crafted HTTP POST request to the vulnerable endpoint /goform/set_LimitClient_cfg with malicious payloads in any of the vulnerable parameters (mac, time1, or time2). The injected commands execute with root privileges on the device, allowing complete system compromise.

The exploitation flow typically involves:

1. Identifying an exposed LB-LINK router on the network
2. Sending a crafted POST request to /goform/set_LimitClient_cfg
3. Including command injection payloads in the mac, time1, or time2 parameters
4. Achieving arbitrary command execution with root privileges

For technical details and proof-of-concept information, refer to the GitHub vulnerability repository.

Detection Methods for CVE-2023-26801

Indicators of Compromise

• Unexpected outbound connections from LB-LINK routers to unknown IP addresses or command-and-control servers
• Anomalous HTTP POST requests to /goform/set_LimitClient_cfg containing shell metacharacters
• Modified router configurations or unauthorized administrative changes
• Presence of Mirai botnet signatures or related malware artifacts on the device
• Unusual network traffic patterns indicative of DDoS participation or botnet activity

Detection Strategies

• Deploy network intrusion detection systems (IDS) with signatures for command injection patterns targeting /goform/set_LimitClient_cfg
• Monitor HTTP traffic to LB-LINK router management interfaces for suspicious POST requests containing shell metacharacters
• Implement web application firewall (WAF) rules to block requests with command injection patterns
• Analyze router logs for unusual access patterns to the vulnerable endpoint

Monitoring Recommendations

• Enable logging on network devices to capture all HTTP requests to router management interfaces
• Set up alerts for any access attempts to the /goform/set_LimitClient_cfg endpoint from untrusted sources
• Monitor for indicators associated with Mirai botnet activity, as documented in Akamai's analysis
• Regularly audit router configurations for unauthorized changes

How to Mitigate CVE-2023-26801

Immediate Actions Required

• Restrict access to router management interfaces to trusted networks only using firewall rules or network segmentation
• Disable remote management interfaces if not required for operational purposes
• Monitor affected devices for signs of compromise and isolate any suspicious systems
• Consider replacing end-of-life or unsupported LB-LINK devices with actively maintained alternatives
• Implement network-level controls to filter malicious requests before they reach vulnerable devices

Patch Information

At the time of this writing, no vendor security advisory or official firmware patch has been published for the affected LB-LINK router models. Users should contact LB-LINK support for updated firmware information and monitor vendor communications for security updates.

Workarounds

• Place router management interfaces behind a VPN or on an isolated management network
• Implement access control lists (ACLs) to restrict which IP addresses can reach the web management interface
• Deploy an upstream firewall or reverse proxy that filters requests containing command injection patterns
• Disable the web management interface entirely and manage devices through alternative methods if available

# Example: Firewall rule to restrict access to router management interface
# Block external access to router management port (commonly 80 or 443)
iptables -A INPUT -p tcp --dport 80 -s ! 192.168.1.0/24 -j DROP
iptables -A INPUT -p tcp --dport 443 -s ! 192.168.1.0/24 -j DROP