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

CVE-2026-6799 Overview

CVE-2026-6799 is a command injection vulnerability affecting Comfast CF-N1-S routers running firmware version 2.6.0.1. The flaw resides in the /cgi-bin/mbox-config endpoint when invoked with method=SET§ion=ping_config. Attackers can manipulate the destination argument to inject arbitrary operating system commands. The attack is initiated remotely over the network and requires low-level authentication. Public exploit details have been released, increasing the risk of opportunistic exploitation. The vendor was contacted prior to disclosure but did not respond. This vulnerability is classified under [CWE-74] (Improper Neutralization of Special Elements in Output Used by a Downstream Component).

Critical Impact

Authenticated remote attackers can execute arbitrary commands on affected Comfast CF-N1-S routers, potentially gaining full control of the device and pivoting to internal networks.

Affected Products

• Comfast CF-N1-S router firmware version 2.6.0.1
• Endpoint component handling /cgi-bin/mbox-config requests
• Web management interface processing ping_config section parameters

Discovery Timeline

• 2026-04-21 - CVE-2026-6799 published to NVD
• 2026-04-29 - Last updated in NVD database

Technical Details for CVE-2026-6799

Vulnerability Analysis

The vulnerability exists in the router's CGI handler at /cgi-bin/mbox-config. When the handler processes requests with method=SET§ion=ping_config, it accepts a user-supplied destination parameter intended to specify a ping target. The application passes this value to an underlying shell command without sanitization or input validation. Attackers can append shell metacharacters such as semicolons, backticks, or pipe operators to break out of the intended command context. Successful exploitation yields command execution under the privileges of the web server process, which on consumer routers typically runs as root. The EPSS score of 1.409% (80th percentile) reflects elevated exploitation likelihood given that a public proof-of-concept exists.

Root Cause

The root cause is improper neutralization of special elements within the destination argument before its inclusion in a downstream system call. The firmware does not enforce a strict allowlist of characters or validate that the input represents a legitimate hostname or IP address. This pattern is common in embedded router firmware where developers concatenate user input directly into system() or popen() calls.

Attack Vector

The attack vector is network-based and requires low privileges on the device's management interface. An attacker who can reach the router's HTTP interface — either from the local network or via an externally exposed management port — sends a crafted POST or GET request to /cgi-bin/mbox-config?method=SET§ion=ping_config. The request includes a destination field containing both a valid-looking target and a command injection payload separated by a shell metacharacter. The router parses the request, executes the underlying ping command, and inadvertently runs the injected payload. Because public exploit code has been released, attackers do not need original research to weaponize this issue.

For technical specifics, refer to the GitHub Vulnerability Report and the VulDB Vulnerability #358492 entry.

Detection Methods for CVE-2026-6799

Indicators of Compromise

• HTTP requests to /cgi-bin/mbox-config containing method=SET§ion=ping_config with shell metacharacters (;, |, `, $()) in the destination parameter
• Unexpected outbound connections originating from the router to attacker-controlled infrastructure
• New or modified files in writable router directories such as /tmp or /var
• Unusual processes spawned by the router's httpd or CGI handler process

Detection Strategies

• Inspect web server access logs on affected routers for requests targeting the mbox-config CGI endpoint with abnormal destination values
• Deploy network signatures on perimeter devices that flag HTTP requests containing command injection patterns directed at router management interfaces
• Monitor DNS and outbound traffic from network infrastructure devices for connections to unexpected destinations

Monitoring Recommendations

• Centralize router and network device logs into a SIEM for correlation and historical analysis
• Baseline normal management traffic patterns and alert on deviations such as off-hours configuration changes
• Track firmware versions across deployed devices and prioritize alerts from hosts running vulnerable Comfast CF-N1-S builds

How to Mitigate CVE-2026-6799

Immediate Actions Required

• Restrict access to the router's web management interface so it is reachable only from trusted management VLANs
• Disable WAN-side administrative access if it is currently enabled
• Rotate administrative credentials for the affected devices to limit risk from credential reuse combined with the required low-privilege access
• Inspect router configuration and connected clients for signs of tampering or unauthorized changes

Patch Information

No vendor patch is available at the time of publication. According to the disclosure record, the vendor was contacted but did not respond. Organizations operating Comfast CF-N1-S 2.6.0.1 devices should treat the issue as unpatched and rely on compensating controls until firmware updates are released. Monitor the VulDB entry for future updates.

Workarounds

• Place affected routers behind a network firewall and block external access to TCP ports used for HTTP/HTTPS management
• Segment the router's management interface onto a dedicated administrative network with strict ACLs
• Replace affected Comfast CF-N1-S devices with vendor-supported hardware that receives timely security updates if no patch is forthcoming

# Configuration example: block external access to router management interface
# Example iptables rule on an 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

# Allow only the management subnet
iptables -I FORWARD -s 10.10.10.0/24 -d <router_ip> -p tcp --dport 443 -j ACCEPT