CVE-2026-3798: Comfast CF-AC100 Firmware RCE Vulnerability

CVE-2026-3798 Overview

A command injection vulnerability has been identified in the Comfast CF-AC100 wireless access controller running firmware version 2.6.0.8. This vulnerability exists in the function sub_44AC14 within the Request Path Handler component, specifically affecting the /cgi-bin/mbox-config?method=SET§ion=ping_config endpoint. Successful exploitation allows remote attackers with administrative privileges to inject and execute arbitrary system commands on the affected device.

Critical Impact
Remote command injection vulnerability in network infrastructure device allows authenticated attackers to execute arbitrary commands, potentially compromising network security and enabling lateral movement within the network.

Affected Products

Comfast CF-AC100 Firmware version 2.6.0.8
Comfast CF-AC100 Hardware

Discovery Timeline

2026-03-09 - CVE-2026-3798 published to NVD
2026-03-10 - Last updated in NVD database

Technical Details for CVE-2026-3798

Vulnerability Analysis

This command injection vulnerability (CWE-77) stems from improper input validation in the ping configuration functionality of the Comfast CF-AC100 router. The affected function sub_44AC14 processes user-supplied input from the /cgi-bin/mbox-config endpoint without adequate sanitization before passing it to system command execution routines.

When a user configures ping settings via the web interface, the device accepts parameters that are directly incorporated into shell commands. An attacker with administrative access to the web interface can craft malicious input containing shell metacharacters or command separators to inject arbitrary commands that execute with the privileges of the web server process.

The vulnerability is classified under CWE-74 (Improper Neutralization of Special Elements in Output Used by a Downstream Component) and CWE-77 (Improper Neutralization of Special Elements used in a Command), indicating that the root cause involves insufficient filtering of special characters that have meaning in command-line contexts.

Root Cause

The fundamental issue lies in the sub_44AC14 function's failure to properly sanitize user-controlled input before incorporating it into system commands. The ping configuration handler accepts parameters such as target hostname or IP address and passes them directly to underlying shell commands without escaping shell metacharacters like semicolons (;), pipes (|), backticks (`), or command substitution patterns ($()).

This lack of input validation is a common vulnerability pattern in embedded network devices where developers may prioritize functionality over security, particularly when assuming administrative users are trusted.

Attack Vector

The attack requires network access to the device's web management interface and valid administrative credentials. An authenticated attacker can manipulate the ping configuration parameters through the /cgi-bin/mbox-config?method=SET§ion=ping_config endpoint.

The vulnerability can be exploited by including command injection payloads in parameters that should contain legitimate ping configuration values. Since the exploit has been publicly disclosed, detailed exploitation techniques are available in the GitHub PoC Repository.

The attack flow involves:

Authenticating to the CF-AC100 administrative interface
Navigating to the ping configuration functionality
Injecting malicious commands through vulnerable parameters
Commands execute with the privileges of the web application process

Detection Methods for CVE-2026-3798

Indicators of Compromise

Unusual outbound connections from the CF-AC100 device to external IP addresses
Unexpected processes running on the device not associated with normal router operations
Modified configuration files or newly created files in system directories
Log entries showing abnormal requests to /cgi-bin/mbox-config with unusual parameter values

Detection Strategies

Monitor HTTP access logs for requests to /cgi-bin/mbox-config?method=SET§ion=ping_config containing shell metacharacters such as ;, |, $(), or backticks
Implement network-based intrusion detection rules to identify command injection patterns in traffic to CF-AC100 devices
Deploy web application firewalls (WAF) with rules specifically targeting command injection payloads

Monitoring Recommendations

Enable comprehensive logging on all Comfast CF-AC100 devices and forward logs to a central SIEM solution
Configure alerts for administrative login attempts from unusual IP addresses or during non-business hours
Implement network segmentation to isolate management interfaces from general network traffic
Regularly audit administrative access credentials and remove unnecessary accounts

How to Mitigate CVE-2026-3798

Immediate Actions Required

Restrict network access to the CF-AC100 management interface using firewall rules or VLAN segmentation
Limit administrative access to trusted IP addresses only
Review and audit all administrative accounts, removing any unnecessary privileges
Monitor device logs for any indicators of exploitation attempts

Patch Information

The vendor (Comfast/Encomfast) was contacted regarding this vulnerability but did not respond. As of the last modification date (2026-03-10), no official patch has been released. Organizations should contact the vendor directly for firmware update availability or consider alternative mitigation strategies.

For additional technical details, refer to VulDB #349765 and the associated VulDB CTI #349765.

Workarounds

Place the CF-AC100 management interface on an isolated management VLAN not accessible from untrusted networks
Implement a reverse proxy or WAF in front of the management interface with input validation rules to block command injection patterns
If ping configuration functionality is not required, disable access to the affected endpoint through network-level controls
Consider replacing vulnerable devices with alternatives from vendors with responsive security practices

bash

# Example: iptables rule to restrict management access to trusted IP only
iptables -A INPUT -p tcp --dport 80 -s 192.168.1.100 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP