CVE-2025-1610: Lb-link Ac1900 Firmware RCE Vulnerability

CVE-2025-1610 Overview

A critical OS command injection vulnerability has been identified in LB-LINK AC1900 Router firmware version 1.0.2. This vulnerability exists within the websGetVar function located in the /goform/set_blacklist endpoint. Attackers can exploit this flaw by manipulating the mac or enable arguments to inject arbitrary operating system commands, potentially leading to complete device compromise.

Critical Impact

Remote attackers with low privileges can execute arbitrary OS commands on affected LB-LINK AC1900 routers, potentially gaining full control over the network device and using it as a pivot point for further attacks.

Affected Products

• LB-LINK AC1900 Firmware version 1.0.2
• LB-LINK AC1900 Router hardware

Discovery Timeline

• 2025-02-24 - CVE-2025-1610 published to NVD
• 2025-11-04 - Last updated in NVD database

Technical Details for CVE-2025-1610

Vulnerability Analysis

This vulnerability is classified as an OS command injection flaw (CWE-78) with an underlying command injection weakness (CWE-77). The vulnerable endpoint /goform/set_blacklist processes user-supplied input through the websGetVar function without adequate sanitization. When the mac or enable parameters are manipulated, the unsanitized input is passed directly to system command execution routines, allowing attackers to inject and execute arbitrary shell commands with the privileges of the web server process—typically running as root on embedded devices like routers.

The vulnerability is remotely exploitable over the network and requires only low-level privileges to execute. The vendor was contacted regarding this disclosure but did not respond, leaving affected devices without an official patch.

Root Cause

The root cause of this vulnerability lies in insufficient input validation and sanitization within the websGetVar function. User-controlled data from the mac and enable parameters is incorporated into system commands without proper escaping or validation, creating a classic command injection scenario. The function fails to sanitize shell metacharacters such as semicolons, pipes, or backticks, which can be used to terminate the intended command and execute arbitrary code.

Attack Vector

The attack vector is network-based, allowing remote exploitation. An authenticated attacker with low privileges can craft malicious HTTP requests to the /goform/set_blacklist endpoint, embedding OS commands within the mac or enable parameters. The injected commands are then executed by the router's underlying operating system.

The vulnerability is straightforward to exploit with low attack complexity. An attacker could inject commands using common shell injection techniques, such as command chaining with semicolons or command substitution with backticks. See the vulnerability technical details for additional analysis.

Detection Methods for CVE-2025-1610

Indicators of Compromise

• Unusual HTTP POST requests to /goform/set_blacklist containing shell metacharacters (;, |, `, $()) in the mac or enable parameters
• Unexpected outbound network connections originating from the router to external IP addresses
• Suspicious process execution on the router such as shells, wget, curl, or nc (netcat)
• Modified router configuration files or unexpected cron jobs
• Anomalous DNS queries originating from the router device

Detection Strategies

• Monitor HTTP traffic to LB-LINK routers for requests containing command injection payloads in form parameters
• Implement network intrusion detection rules to identify POST requests to /goform/set_blacklist with suspicious characters
• Deploy behavioral analysis to detect abnormal router activity such as unusual CPU usage or unexpected network traffic
• Review router access logs for authentication events from unexpected IP addresses

Monitoring Recommendations

• Enable logging on network firewalls and IDS/IPS systems for traffic to and from LB-LINK AC1900 devices
• Configure alerts for any administrative access to router management interfaces from non-whitelisted IP addresses
• Monitor for firmware integrity changes using scheduled configuration backups and comparison
• Implement network segmentation to isolate IoT and network devices from critical infrastructure

How to Mitigate CVE-2025-1610

Immediate Actions Required

• Restrict access to the router's web management interface to trusted IP addresses only using firewall rules
• Disable remote administration if not required for business operations
• Place the LB-LINK AC1900 router behind a firewall and limit access to the /goform/ endpoints
• Consider replacing the affected device with a router from a vendor with active security support
• Audit all user accounts on the router and remove unnecessary credentials

Patch Information

The vendor (LB-LINK) was contacted regarding this vulnerability but did not respond. As of the last update on 2025-11-04, no official patch is available. Organizations should implement the workarounds below and monitor for any future firmware updates from the vendor. Additional details are available at VulDB #296600.

Workarounds

• Implement network-level access controls to restrict access to the router's management interface to internal networks only
• Use a VPN for remote administration rather than exposing the management interface to the internet
• Deploy a web application firewall (WAF) in front of the device to filter malicious requests containing command injection patterns
• If feasible, disable the blacklist functionality by avoiding use of the /goform/set_blacklist endpoint until a patch is available

# Example: Restrict access to router management interface using iptables
# Run on a firewall or gateway device protecting the LB-LINK router

# Allow management access only from trusted admin subnet
iptables -A FORWARD -d <ROUTER_IP> -p tcp --dport 80 -s 10.10.10.0/24 -j ACCEPT
iptables -A FORWARD -d <ROUTER_IP> -p tcp --dport 443 -s 10.10.10.0/24 -j ACCEPT

# Block all other management access
iptables -A FORWARD -d <ROUTER_IP> -p tcp --dport 80 -j DROP
iptables -A FORWARD -d <ROUTER_IP> -p tcp --dport 443 -j DROP