CVE-2026-6799: Comfast CF-N1-S RCE Vulnerability

CVE-2026-6799 Overview

A command injection vulnerability has been discovered in the Comfast CF-N1-S router running firmware version 2.6.0.1. The flaw exists in the ping configuration endpoint (/cgi-bin/mbox-config?method=SET§ion=ping_config), where improper handling of the destination argument allows remote attackers to inject and execute arbitrary commands on the underlying operating system. This vulnerability can be exploited remotely by authenticated users, potentially compromising the entire router and any network it manages.

Critical Impact

Successful exploitation allows remote command execution on the router, enabling attackers to take full control of the device, intercept network traffic, modify configurations, or use the router as a pivot point for further attacks on the internal network.

Affected Products

• Comfast CF-N1-S Router Firmware Version 2.6.0.1

Discovery Timeline

• 2026-04-21 - CVE CVE-2026-6799 published to NVD
• 2026-04-22 - Last updated in NVD database

Technical Details for CVE-2026-6799

Vulnerability Analysis

This vulnerability is classified as CWE-74 (Improper Neutralization of Special Elements in Output Used by a Downstream Component), commonly referred to as injection. The affected component is the CGI-based ping configuration handler in the Comfast CF-N1-S router's web management interface.

The router's web interface provides functionality for network diagnostics, including a ping utility that allows administrators to test connectivity to remote hosts. The destination parameter, which specifies the target host for the ping operation, is not properly sanitized before being passed to the underlying system shell. This allows an attacker to inject shell metacharacters and arbitrary commands that will be executed with the privileges of the web server process, typically root on embedded devices.

The exploit has been publicly disclosed and may be actively used in attacks. The vendor was contacted regarding this vulnerability but did not respond, leaving no official patch available at the time of disclosure.

Root Cause

The root cause of this vulnerability is insufficient input validation and sanitization in the ping configuration endpoint. The destination parameter is directly concatenated into a shell command without proper escaping or validation of special characters. This classic command injection pattern allows attackers to break out of the intended ping command context and execute arbitrary shell commands.

Attack Vector

The attack is network-based and requires low-privilege authentication to the router's web management interface. An authenticated attacker can craft a malicious HTTP request to the /cgi-bin/mbox-config endpoint with a specially crafted destination parameter containing shell metacharacters (such as ;, |, &&, or backticks) followed by arbitrary commands.

For example, an attacker could manipulate the destination parameter to append commands after a semicolon or use command substitution to execute malicious payloads. The injected commands would execute in the context of the web server, which on embedded routers typically runs with root privileges.

Technical details and proof-of-concept information are available in the GitHub Vulnerability Report and VulDB Vulnerability Entry #358492.

Detection Methods for CVE-2026-6799

Indicators of Compromise

• Unusual HTTP requests to /cgi-bin/mbox-config with method=SET§ion=ping_config containing shell metacharacters in the destination parameter
• Unexpected processes spawned by the router's web server process
• Unauthorized configuration changes or new user accounts on the router
• Outbound connections from the router to unknown external IP addresses

Detection Strategies

• Monitor web server access logs for requests to the vulnerable endpoint containing suspicious characters such as ;, |, &&, $(), or backticks in URL parameters
• Implement network intrusion detection rules to flag HTTP requests matching command injection patterns targeting this specific CGI endpoint
• Deploy SentinelOne Singularity agents on network monitoring systems to detect anomalous traffic patterns indicative of router exploitation

Monitoring Recommendations

• Enable verbose logging on network firewalls and IDS/IPS systems monitoring traffic to router management interfaces
• Configure alerts for any access to router management interfaces from unexpected source IP addresses
• Review router logs regularly for signs of unauthorized command execution or configuration changes

How to Mitigate CVE-2026-6799

Immediate Actions Required

• Restrict access to the router's web management interface to trusted IP addresses only using firewall rules or the router's built-in access control features
• Disable remote management access if not required, limiting administration to local network connections only
• Consider replacing the affected device with a router from a vendor with better security support practices
• Segment the network to isolate the vulnerable router from critical systems

Patch Information

No official patch is currently available. According to the vulnerability disclosure, the vendor was contacted but did not respond. Users should monitor the VulDB Submission #795203 and vendor communications for any future security updates.

Given the lack of vendor response, organizations using this device should strongly consider migrating to alternative hardware with active security support.

Workarounds

• Implement strict IP-based access controls to limit who can access the router's web management interface
• Place the router behind a firewall that can filter and inspect HTTP requests for command injection patterns
• Use a VPN to access the management interface rather than exposing it directly to untrusted networks
• Monitor network traffic for exploitation attempts and implement automated blocking of suspicious source IPs

# Example: Restrict management interface access using iptables on an upstream firewall
iptables -A FORWARD -d <router_ip> -p tcp --dport 80 -s <trusted_admin_ip> -j ACCEPT
iptables -A FORWARD -d <router_ip> -p tcp --dport 80 -j DROP