CVE-2026-3301: Totolink N300rh Firmware RCE Vulnerability

CVE-2026-3301 Overview

A critical OS command injection vulnerability has been identified in Totolink N300RH routers running firmware version 6.1c.1353_B20190305. The vulnerability exists within the setWebWlanIdx function of the /cgi-bin/cstecgi.cgi component, which is part of the Web Management Interface. An attacker can exploit this flaw by manipulating the webWlanIdx argument to inject and execute arbitrary operating system commands on the affected device. This vulnerability is remotely exploitable without authentication, and a public exploit has been released, significantly increasing the risk of active exploitation.

Critical Impact

Unauthenticated remote attackers can achieve full command execution on vulnerable Totolink N300RH routers, potentially leading to complete device compromise, network pivoting, and persistent backdoor installation.

Affected Products

• Totolink N300RH Firmware version 6.1c.1353_B20190305
• Totolink N300RH Firmware version 6.1c.1349_B20181018
• Totolink N300RH Hardware version 4.0

Discovery Timeline

• 2026-02-27 - CVE-2026-3301 published to NVD
• 2026-02-27 - Last updated in NVD database

Technical Details for CVE-2026-3301

Vulnerability Analysis

This vulnerability represents a classic OS command injection flaw in embedded IoT device firmware. The setWebWlanIdx function within the CGI binary fails to properly sanitize user-supplied input before incorporating it into system commands. When the webWlanIdx parameter is processed, the application does not validate or escape special characters, allowing an attacker to break out of the intended command context and inject arbitrary shell commands.

The Web Management Interface on Totolink N300RH routers exposes the vulnerable CGI endpoint over the network. Since the router's web interface typically runs with root privileges on embedded Linux systems, successful exploitation grants the attacker complete control over the device. The attack requires no prior authentication, making any internet-exposed device an immediate target.

The public availability of an exploit significantly lowers the barrier for exploitation. Threat actors can leverage this vulnerability to install persistent backdoors, intercept network traffic, pivot to internal network segments, or recruit compromised devices into botnets.

Root Cause

The root cause is improper input validation (CWE-77: Improper Neutralization of Special Elements used in a Command, CWE-78: OS Command Injection). The setWebWlanIdx function constructs system commands using the webWlanIdx parameter without sanitizing shell metacharacters such as ;, |, &, $(), or backticks. This allows attackers to terminate the legitimate command and append malicious instructions that execute with the privileges of the web server process.

Attack Vector

The attack is initiated remotely via the network interface. An attacker sends a specially crafted HTTP request to the /cgi-bin/cstecgi.cgi endpoint with a malicious webWlanIdx parameter value. The payload typically includes shell metacharacters followed by arbitrary commands.

The vulnerability can be exploited through crafted HTTP POST requests to the CGI interface, injecting shell commands via the webWlanIdx parameter. An attacker might inject payloads such as command separators followed by reverse shell commands or other malicious operations. For detailed technical exploitation information, refer to the GitHub PoC Repository.

Detection Methods for CVE-2026-3301

Indicators of Compromise

• Unexpected outbound connections from the router to external IP addresses, particularly on non-standard ports
• Unusual processes running on the router such as reverse shells, wget/curl downloads, or netcat listeners
• Modifications to router configuration files or firmware that were not authorized
• HTTP access logs showing requests to /cgi-bin/cstecgi.cgi with suspicious webWlanIdx parameter values containing shell metacharacters

Detection Strategies

• Monitor network traffic for HTTP requests to /cgi-bin/cstecgi.cgi containing shell metacharacters (;, |, &, $(, backticks) in POST parameters
• Deploy intrusion detection signatures that alert on command injection patterns targeting Totolink router management interfaces
• Implement network segmentation to isolate IoT devices and monitor cross-segment traffic for anomalies
• Review router logs for authentication failures followed by successful exploitation attempts

Monitoring Recommendations

• Enable logging on network firewalls and IDS/IPS systems for all traffic destined to router management ports (typically TCP 80, 443, 8080)
• Configure SIEM alerts for patterns consistent with command injection attacks against CGI endpoints
• Periodically audit router configurations and compare against known-good baselines to detect unauthorized modifications

How to Mitigate CVE-2026-3301

Immediate Actions Required

• Disable remote administration access to the router's Web Management Interface immediately
• Restrict access to the management interface to trusted internal networks only using firewall rules
• Check for unauthorized configuration changes or suspicious files on affected devices
• Consider replacing end-of-life or unsupported devices that will not receive security updates

Patch Information

As of the last NVD update on 2026-02-27, no official patch from Totolink has been referenced in the vulnerability data. Organizations should monitor the Totolink Official Website for firmware updates addressing this vulnerability. Given the severity and public availability of exploit code, prioritize remediation efforts accordingly.

For additional vulnerability intelligence, consult VulDB #348052 for ongoing updates.

Workarounds

• Disable the web management interface entirely if not required for operations
• Implement network-level access controls (ACLs) to restrict management interface access to specific trusted IP addresses only
• Place vulnerable routers behind a VPN and require authentication before management interface access
• Deploy a web application firewall (WAF) in front of the management interface to filter malicious requests targeting command injection patterns

# Example: Block external access to router management interface using iptables on upstream firewall
iptables -A FORWARD -d <router_ip> -p tcp --dport 80 -j DROP
iptables -A FORWARD -d <router_ip> -p tcp --dport 443 -j DROP
iptables -A INPUT -s <trusted_admin_ip> -d <router_ip> -p tcp --dport 80 -j ACCEPT